That being said... I've been able to lap a stock engined 2008GT GR40 street car that weighs 3800lbs. around Infineon within 2sec. of the Infineon AI record. The truth is the new S197 chassis is so good that the GR40SS is the most I would as an upgrade. Ditching the crappy rear setup for a Watts/TorqueArm makes a noticeable difference.
For you being a racer, its best explained as it just makes the car less work to drive at the limit, and it allows you to go over the limit without biting your head off. You'd really have to drive one to see what I mean. But after working there for a few years, thousands of miles of testing driving GR equipped cars and then driving a new 2010 Miller Car I can still tell the difference.
Besides as you know... it usually comes down to the nut behind the wheel.
Darrell Anderson has destroyed the NASA AIX/SCCA ITE lap record for every track he has raced at. He took 6 seconds out of the old Infineon record, from a 1:45 to a 1:39. Laguna, Thunderhill...
Fun video of him running down a $250K 700HP twin turbo $250K:
http://www.youtube.com/watch?v=33ZklC0pjmE
Colin