tbh it's one of those things that it takes $$$ to play..
popular mods, are svt header, orp, flex, exhaust, intake, and tune.. the latter being the most expensive but makes a difference. also throttle body will give you a better throttle response. best way to save money is to keep an eye out on our forum here at the BST section.. a lot of good deals have been popping up.
fswerks, cfm, massive, focus-power, topspeed, and rps make parts for our cars and most of em are vendors here.
2000 Turbo Zx3
2003 Pitch Black SVT
2000 SPI 220k miles all original THE UNICORN
Focus Revolution Club