for the 500 range the best bet is to look for a used one. i'm not sure if anyone here is getting rid of one but i'm sure there are a few on nasioc in that range. a few of the top ones are the hks ti, invidia, borla, cobb, stromung, turbo xs, and a few more.

snowman is one of the guys here on the board that tunes using the enginuity program. you don't need to buy an actual engine management system but just pay snoman to do his magic.