My impressions so far.. after 10-minute testing a lot of cars, japanese, american and english I think that I have made my choice. The 10-minute session with that car became longer and longer until after 300kms I ended up with clean T2 mid-45:s.
At first I got surprised that I could go around the track faster with sports-suspension and racing muffler than with semi-racing suspension and sports muffler, but the extra few horsepower gained was not so important. The big difference was that the power-band of the engine was moved up on higher revs so it suited red-line shifting better. It made up the loss of grip and shaved the lap-time with ~0.5 sec.
What tires are you running? I'm using T7:s, have tried T8:s but I cant find them worth that 12.000 extra.
/D