If you are racing on a track, suspention will be your most worth while upgrade.
Most engine mods people start with are:
-Forced Air Induction Kit (more, COLDER air put into the throttle. The key to this is as much air as possible, and as cold air is DENSER, it is more faavourable)
-Stainless steel De-Cat exhaust (removing the catalytic convertor increases the air flow, as does stainless metal, as gasses flow more swiftly across them)
-Stainless Steel Manifold (same principle as exhaust system)
-Fast road cams (these have a greater angle, therefore opening the valves further than normal cams. Also they will be stronger to withstand the extra bhp you are putting through your lump.
-An ECU Remap (the garage will change the setup of your car's 'computer' so that more fuel is put through the injectors, to balance out the extra air intake from the new induction kit.)
19" Wheels will make your car accelerate SLOWER than it already is and probably reduce the amount miles per gallon you get from your car currently!
THIS IS ONLY A GENERIC GUIDE TO WHAT PEOPLE NORMALLY MOD ON THEIR CARS FIRST. If someone else owns an Audi then maybe they can help you out further. So hang on for more information.