For example, the collision physics are just as bad as they've ever been since the first Shift, some cars have almost retarded levels of understeer (the Z4 GT3 and the M3 as well) and other still feel like boats (the Lancer Evo X). Then you have the camera effects and sense of speed, there's no connection between what the car is doing physically and what you're looking through the windshield. I don't understand this, even Shift 2 was more convincing in that aspect.
Collision physics are not driving physics. I don't find them to be that bad, but each to their own.
The camera effects and FOV are all tweakable. I'm guessing you're using stock settings, which unless your TV is a certain size and a certain distance from where you're sitting are not correct. If you don't have access to the iRacing calculator, tell me what size your screen is and how far you sit from it and I can tell you what FOV will be accurate for you.
If you haven't used an accurate FOV before it can be a bit weird, but it does help your driving and it does mean that once you know it you can set all games up to have the same sense of speed. Which helps a lot.
I went and drove the cars you mentioned. Tested on Watkins Glen, because going over the rise on the S and the carousel with it's falling away can tend to provoke understeer in susceptible cars.
The Mitsubishi is a dog. A total dog. However, looking at the relevant threads I find that it's still Beta 1, so the physics are still in progress. It also doesn't have the central diff implemented, nor any of the fancy electronic aids that make Evos so special. Add that to 400hp with a silly large turbo and I'm not entirely surprised it's a dog. I could sort of get it working sometimes, but then it would just slide off into the scenery in a cloud of smoke.
The Z4 I found to be not bad. Huge amounts of rear grip meant I could stomp the throttle really early out of corners, but the nose still tucked in nicely when I feathered it. The couple of times I lost it was to oversteer, and there was never a moment where I was cursing understeer. It didn't feel quite right to me and was quite twitchy, but I'd be pursuing that through setup as it felt like more of a personal style thing than anything actually wrong with the car.
There are two M3s, so I tested both.
The GT4 M3 GTS is an odd little car. It felt very skittish to me, but it was definitely pointy. Far less grip at the back than the front, and I had no trouble getting it to turn in and go where I wanted. Definitely not understeery, and definitely requires care with the right foot. Not that fun to drive though.
The M3 GT (is it a GT2 from memory?) is amazing. Amazing. The balance is outstanding, it moves to every slight throttle movement, turns in sharply, not twitchy, can get on the power early. Unbelievably pleasant to drive. I was trying to monster some of the curbs to upset it, hardly did a thing. If you're not enjoying that, I don't know what to tell you. That's one of the best feeling cars I've driven in any game in a long time.
Are you on the monthly builds or weekly? I'm on the weekly ones, so that could account for some discrepancy. They do change setups and tyres fairly regularly, so I'd imagine with a monthly build it'd be easy to get unlucky and get stuck with a dud set.