If I had 900 for power mods....
1) cams. stage 1 if you're going to turbo later, stage II if NA all the way.
Thats 900+ some inc install.
peak hp 180 (+14 or was that 15?)
2)Catback exhaust $400ish
3) borla headers.
peak hp ~189ish.
FWIW if you have a chunk of cash now, do the cams as its easier to pick up the small bits along the way.....