Hi all i will be gettin some tax money back soon and i was just currious which one will be the wisest investment.

I really dont want to open up my motor, as it is my daily and i want to keep it reliable and still get fairly good mpg. I was thinking of getting some:

Crane Cams race roller rockers for about $309 in summit. but will i also need different studs and pushrods?
and maybe a k&n fipk i can get it for about $230 at autozone

or SLP loudmouth ($350) and some edelbrock shorty headers for about $330-plus install

I mean i already have an SLP lid with a k&N filter and i have a slp y pipe as well as flow master muffler, but i just want to get all the mods that will increase power as well as mpg. Such as headers and exhaust. I originally was thinking FIPK and loudmouth but the roller rockers seem like a wise investment that could yeild up to 24 hp. Let me know what you guys think