Go to gamefaqs.com and look for a tuning guide by Big-D. Use his "Unstable Turning" settings for your suspension, and gear the transmission according to his "Pure Acceleration" setup. You may need to fiddle around with the 6th gear to achieve your ideal top speed.
Ignore his setups for Limited-Slip, ASM, TCS and use what works best for you.
Personally, I turn the Limited-Slip Initial Torque and Deceleration all the way down, and increase the aceleration side-effect by 2 to 5.
ASM to 1 and TCS to 1 per 100 Hp the car makes.
If you need the suspention and trans settings, PM me and I'll get them to you ASAP.