Skunk 2

Skunk 2 pro series intake manifold and skunk2 68 mm throttle body worth 5 to 10 horsepower on a b18b1. or what would you suggest for 500 dollars want to stay n/a

the IM and T-body are only going to give you those gains if you already have stuff done to your engine. You'll end up losing low end power if you put those on. Look for stuff more along the lines of header, intake, and exhaust.

Already have i/h/e

then some cams would be good. Stage 1 Crower cams should be enough for some decent gains, and you won't have to buy the upgraded valvetrain.