Fully tuned (less race modification) I count it as the tied-for-sixth fastest Skyline. R34 GT-R V-Spec best, then R34 GT-R, Mine's R32.5, R33 GT-R '95, R32 Tommykaira, and tied with NISMO 400R '97. R34 Tommykaira probably about as good with less power but lower rideheight and better tires. Still a great car, but buried under too many similar but better options, so 50/100.
Although probably your testing was more thorough than mine (there are some threads with results, IIRC), I also tested some cars via hotlapping SSR5 in fully tuned state, and I have to say that my experience with GT-Rs is little bit different. The factory R34s are the fastest no doubt, but after them there comes suprising Nismo 400R, then R33 V-spec, then R32 '89, and only after them Mine's machines follow, lead by R34. Which is the reason I said it is better IRL - in Hot Version videos it was almost unbeatable among tuned GT-Rs, and in the game the engine is tuned actually worse than in Nismo-tuned cars (Tommykairas suffer from similar problem).
Probably these results are the case because of tuning setup I use on GT-Rs.
Also I am not quite sure about the engine glitch you mentioned - I race the '97 R33 V-spec regularly and it does everything right. I know that the GT-R LM has almost useless engine because of unnaturally low rev-limiter and too peaky powerband, but that's it.
On the Lexus - I like this car: handling is decent for a luxury saloon, the engine is nice and smooth, although maximum power is not impressive. I could give it high score, but it has the major disadvantage - Aristo V300 '98, the ultimate sleeper of GT2.
So i give Lexus 65/100.
In the end, I turned my GS400 into fantasy Lexus V8 Supercar hybrid, and with over 640 hp it is quite fun to drive
Next - Hakosuka GT-R (KPGC10)