If you're going to make any power out of your vehicle, you have to be able to put it on the ground and upgrading your clutch is one of the most important aspects of your drivetrain.
A lighter flywheel with reduce the rotating mass sucking power away from your engine. By reducing weight here, your engine will rev quicker and more freely.
Tired of only spinning one wheel? Installing a limited slip differential will solve this problem. Applying power to both drive wheels is easily done with one of these. This will create a better launch and more traction coming out of turns.
Driveshafts and stainless steel clutch lines both very good upgrades to any performance car. Maximize the amount of power you can put to the ground and create a better clutch pedal feel with these.
Reducing your vehicles shift throw will result in quicker more responsive shifts. Easy to install, these are very good upgrades to any manual transmission car.
For you guys and gals running automatics, increase your engines launch speed by installing a higher stall torque converter from B&M. Harder launches are easily acheived with the addition of these converters.