As Shells said Sylux, some cars have same bhp as GT5, but a lot are different now requiring new tunes. I've had success tuning some cars like i did on GT5 with the same bhp.
So i was testing out the camber and toe theory AGAIN last night. I've seen a good friend of mine using camber, he's a top tuner and respected but i didn't ask him about it yet.
So i used some toe in toe out on my rx7 spirit, and i swear i was topping out a few feet before the shadow of the bridge @ 152mph. Without toe i was topping out a couple feet after the shadow. Now i tested this with the same tune with and without Toe. I also had bit of camber on it too.
Maybe its just my imagination and just the tune and the gear shifting, so don't go taking anything i've said as fact - as shells said we can't properly test the theory for sure, until a speed test.
The general consensus at the moment is that min min ride height helps pull on 4WD. But then again some RWD cars also like min min ride heights, not all like max max. dampers seem to make a more of a different in travel now.
Be careful when changing rims, my RUF CTR2 i changed the rims and my tune that worked perfectly before had a 1st gear massive bog. So i had to reflip it and tune i over again.
Heres a really useful tool for you. Since you can no longer see what top speed your flipping your transmission to.
Max Speed Slider / Lowest Final Gear
For e.g
112mph / 2.500 = 44.8mph
44.8mph x (Your Flip Number)
E.g
44.8mph x 3.400 = 152.32mph
Take these figures and then for GT6 add 10-15mph to compensate. So you might have to reflip to a slightly higher final gear to get the actual top speed you want for the kind of trap speed you are looking to get.
I hope what is said here helps you silux. One more thing, on Muscle cars or most RWD using comfort softs seems to help the generate lesser friction and helps the run. But i'm not sure if this works on 4WD's.
Also even though Wings don't appear to make any real difference, take them off anyway theirs a chance they could affect performance however little. Wings add unwanted levels of downforce sometimes which might help the launch of the car but not the pull.