[djomlas]

you really cant squeeze anything out of the 2.5 realistically.
if you want to just spend a little $ on it thats fine, get a EVO intake for great sound and an exhaust, and you can also get the headers (now they are really cheap, and when u get the new motor, just sell them on ebay for almost the same price).

but definitely get a short shifter for it, 2.5 or anything else, stock is just too hilarious after you install the short shifter.

also, since the upgrade is in place, get the strut bars, they will help with the handling, and different wheels and/or brake upgrade...possibly some cospetic mods like sideskirts/bumpers and such, those will just complete the picture

good luck with your mods man