Below is my project list... I don't regret a single upgrade
As for what I'd do first... the car needs to be usable/reliable on the track... that means
1. oil cooler... stillen 'race' setup or custom dual setup
2. baffling inside fuel tank or swirl pot to resolve fuel starvation issue... I'm still working on this
Then work on the weight
3. take 150 lbs of weight off by reading weight reduction thread
4. relocate battery to rear
then cheap suspension upgrades
5. stiffer/adjustable anti-sways
6. rear camber arms
then cheap horsepower
7. CAIs
8. skip the HFCs and go straight for resonated test pipes
then all the rest! I really enjoy the lightened flywheel and real LSD
