Look at it this way.
A 160hp 4 cylinder that is 140 cubes is pretty good.
That Chebby of yours has a motor 2.5x larger.
If we were talking efficiency, a Mazda made motor that size.
400hp would be happening...stock...without a supercharger.
Seriously though, an intake might get you 5-10, an exhaust maybe another 5.
These things are pretty damn efficient from the factory, so it's pretty hard to squeeze out any horsepower without going boosted.
I get about 250 out of my Garrett GT28R on the Miata, which isn't a lot, but when you add the fact it weighs under 2500 pounds with a hardtop on, that's a pretty good number for scaring stock Camaro boys.
Just remember no replacement for displacement, and what the others suggest is true, it is always more expensive to do horsepower going naturally aspirated, the others are cheaper per hp, but cost a lot more. Figure $3k for a SC, and $5k for a decent turbo kit. I'd probably spend $500 and do the intake and have a shop custom up an exhaust and leave it. Neither will trash the warranty, and that will give you an edge on anyone else that rolls up on you with a 3 that gets frisky.
