Some testing done, I intend to try to give cars more laps after the first cycle is complete and I've learned stuff. DC in notes so far but holding until I've completed a cycle.
Testing done primarily with G27, MT. Some very quick checks sometimes done with DS3 to check characteristics where the tuner is known to have used a DS3, but complete laps all wheel-based.
I tend to try the limits (mine, anyway) for a bit, which usually results in crashing and burning a lot. Also, if I'm complaining in some way about doing things badly myself (bleeding too much speed, not using all the aero grip) or silly stuff like complaining about the width or speed of the car, don't worry, that's just me talking out loud, not criticizing.
ACSR421 Ford GT LM Spec II Test Car
Car is well set up for the track. Gears and balance are good, speed is excellent; very good through the Lesmos, and Chicane 2. Took me a little bit to extract the goods through Ascari, partly to do with the low downforce tradeoff, but also very good for Parabolica. Only concerns for me were the torque taking me by surprise out of chicane 1 (not unusual to have to be careful here), and brake/turning chewing the fronts for Parabolica, but a quick test with a DS3 shows me that's a feature; might be able to mitigate it with technique with more time, if necessary, or just tweak the BB in-race. Possibly a problem for longer races with tire wear on, since the heat would be magnified, but likely a necessary tradeoff for the high speed turn-in, especially on DS3; can't really fault it for that in this test environment, anyway, unless it's hurting lap times.
Getting back into this, I was enjoying it right away, and back up to speed very quickly.
Time: 1:39.646
DC: Outstanding
Motor City Hamilton Ford GT LM Spec II Test Car
Car is the fastest in both acceleration and top speed tested so far. Interesting study in contrast with ACSR's - the throttle is easier to use, but it was for me on balance just a bit harder to extract a fast time from the car - then again, it was a faster time. Part of that was, I admit, due to the car being fast enough that it messed with my braking points, turn 1 especially. Setup wise, I found it harder to use in chicane 1 (turn in fine, track out tricky, but throttle/gears a bit easier) and the Lesmos, but easier in Ascari and Parabolica. It also did not exhibit the same amount of tire squeal under braking, but it was perhaps slightly more scary under brakes but less under power. Might be a better race setup with wear.
Jumping back in, also able to get back up on my ghost very quickly, and saw the tenths possible to beat it by, but was not able to do it without error in the few laps available. This tune is definitely a little safer and slightly less pointy than ACSR's, and possibly a little less "fun", but not to the point it's not chuckable and enjoyable in its own right.
Time: 1:39.370
Only a little left in this for me. Still, might even see a 38 if lightning strikes again, and harder.
DC: Outstanding
This car does have a nasty habit of being both efficient and fun to drive. Good noise, too.
ugabugaz Zonda LM Race Car
The car is well set up all over the track, with one problem - the throttle is touchy. I like to think I'm getting better at throttle control, but I'm still secretly a throttle masher at heart. I'm losing a bunch of time in the chicane with this currently. Barring throttle complications, the car is good in chicane 2, not bad in the Lesmos (the throttle steering is helping it here when I don't overdo it), very good balance in Ascari, and not bad in Parabolica. One advantage it does have is that the gearbox is very well set up for the track corner profiles - best so far in that regard for me; I'll re-examine the others later. The oil light is on in this car; I assumed this was deliberate (I rebuilt my RX knowing full well it was bad for speed, but wanted better comparisons), and did not trouble myself to check whether it was losing HP during testing.
Getting back in, took a few restarts to find the throttle technique again, but was pretty consistent after that.
Time: 1:40.005. Yes, I beat the last one by exactly .001, after messing up Ascari while being 1-3 tenths up
DC: Driveable (would be Outstanding with just a tiny bit less scare on the right boot; it would certainly keep me awake in a long race. Mind you, I've driven the Zonda R around here on R1s at 775bhp for an hour.)
XDesperado67 M3 GTR Race Car
Very safe and easy to use, with the one exception of exiting Ascari. I don't think I've got it right for this car yet. Throttle is pretty easily mashed compared to others, and if anything, the car is a little bit too stable - just a touch (more?) of throttle steering would probably do it good. It accelerates well, but is hurt by the lack of top end speed. Gear set is good, brakes are very good. Would be a good enduro ride if I work out what I'm doing wrong in Ascari; still got some work to do in Chicane 1 on the best lap done so far.
Getting back in, took a few restarts to adjust to push in Parabolica. Found ghost pace again, didn't match it, though; Ascari exit too timid on the lap I was up.
Time: 1:40.783
DC: Driveable
Onboy123 Camaro LM
Really liked the colour. 
Braking is indeed a bit wild, but effective. Throttle, though, is mild. Found it a bit tricky to balance into Chicane 2 (Roggia) for some reason (probably my style/approach), but otherwise OK. Found it oddly hard to re-adjust to the better corner speed and braking distances available after some of the others, but that's hardly your fault.
Second try, much like the first. Pretty driver-friendly, but I couldn't better the lap time fast enough.
Time: 1:40.860
DC: Driveable
krenkme BMW M3 GTR Race Car '01
Slightly easier to use but slightly slower (top end/accel) than XDesperado's for me. Liked the diff a little more - helped it round a couple of the bends, but suffers slightly due to slower speed. Very, very easy to use, and a very enjoyable drive.
Second outing - no improvement, but I did find out that this car was really, really easy to pick up again. There's a reason I prefer slight oversteer to understeer at Monza; undertsteer tends to kill the fronts, and will at some point dump me into the kitty litter. Or one of the speed signs after Lesmo 1 (splat). Not a danger here, nicely balanced for me.
Time: 1:40.874
DC: Outstanding
Ridox2JZGTE Lexus IS-F RM
Likes going fast. Does not much like turning; that's the tradeoff. Chassis (pre-tuning) tends to understeer, which seems to have been dealt with OK, but the LSD is set for inside tire fire, and BB is apparently calibrated for ABS 0 on a controller I don't have; the high BB renders threshold braking risky for me (with ABS off), lacking pedal range to do it, and even tends to squirm the tires under ABS. Lap times with ABS 1, per rules; but testing between BB 4/2 to 6/4 revealed this (no ABS) is what would probably be necessary to take some corners at speed, at least on a wheel. Only car that really tended to push wide for Parabolica. Suspension setup seemed good, but my style didn't get on with the diff and brakes. Could possibly have stood to flatten the peaky power band a little for more aero, maybe?
Time: 1:42.110 so far.
DC: Holy Crap
CSLACR Chevrolet Corvette C5-R (C5) '00
No muss, no fuss. Just not enough guts. Nicely set up everywhere - again, having trouble utilizing all the available grip and cornering speed after doing without; brakes very well indeed, and I'm often carelessly dropping speed too much, but I'd certainly get used to it again. Gears and LSD very good. I really like the car, and have used it before at the slightest excuse.
Second go like the first one. Lap looks OK when chasing it, still feels good everywhere.
Time: 1:41.758
DC: Outstanding
C-ZETA GT by Citroen Race Car
Really fast considering the aero level used (all of it). Still surprising amounts of torque; apart from adjusting to the diff, found it pretty easy to use everywhere, with the usual caution in chicane 1. Odd 7th gear also took some getting used to. Also forgot completely quite a few times how wide this thing is; touching grass is bad, m'kay. I think that this car was possibly the outright fastest available (in terms of speed given a hp figure).
Coming back, frustrated myself by dumping 2-3 tenths up 2-3 times in a row. Had to give up; my apologies. For some reason I was uncomfortable into Parabolica, though the real problems were Ascari (mostly) and Lesmo 2.
Time: 1:40.432
Lousy Roggia (chicane 2); Was at least an easy .2-.3 left in this (just didn't get it in time), plus the usual more everywhere for refinement. You know, the kind Johnny has and I don't.
DC: Driveable
Johnnypenso Dodge Viper GTS-R Team Oreca Race Car '00 #91
Pretty easy to use, and fast to boot. Only real issue I was having with it is getting into the slot (that's what she said) in Ascari. Probably just too tired. Anyway, I did have a slight feeling of being driven in this rather than driving; would indeed be a very solid race setup, but although I do like the car, it doesn't give me a whole lot of room to explore; a little safer than the Fords, but that actually caused me more issues with (what I assume was) my own errors when I couldn't get it back; I'm probably creating some understeer through less deft braking and slip angle use.
Time: 1:39.700
DC: Driveable
ealirendur RX-7 LM
Coming back to this cold, I can definitely see where the howls of anguish are coming from. But then I start to get used to it again, and the smile I get when it kicks into the chicanes stays on my face. Also, once adjusted, am pretty consistent with this.
Time: 1:40.143.
Had two tenths off this with a tire over, in a not-particularly fast chicane.
DC: Driveable. On review, need to maximise the car a bit better without losing too much agility.
Final
I did jump into the ITR TC, with the extra 5 clicks of front downforce…and extra power…and less torque…and easier to handle chassis…but still. 
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