the dodge viper is stock...on the civic I changed the Heatsink on the engine so the engine doesnt get overheated too quick...I changed the stock muffler to a dual chromed out muffler(its loud as shit), I changed the stock filter to a K&N filter for more air flow to the engine...I changed the suspension so the car doesn't bounce around...changed most of the plastic pieces that connect to the wheels to anodized purple aluminum so they don't break as easy and their tighter for better handling...
...I could do an "engine swap" and put a bigger engine but that'll be about 200 bucks...