So after reasearching for hours, and talking to some other chevy guys in person, here is what I have concluded.

I have a 91 305 tpi

Parts I'm looking at buying:
2460 Hooker Headers and Y pipe 10-20hp
LT1 Cam with new valve springs 30-50hp
Full magnaflow 2.5" cat back 10hp
High Flow Magnaflow cat 3-5hp


I need someone to second on the HP numbers I have found from old threads before I actually buy all of these parts. Or just give me a total hp gain estimate.

Will these upgrades make my car feel like a whole different car?

 

You might get the 30 HP out of the cam change if you do the exhaust. It isn't additive.

The 2.5" exhaust is barely worth the effort, and certainly not worth the cost. Go for the better headers and Y-pipe, the Hooker 2055HKR, and 3" cat/exhaust from there.

If you do go with the better exhaust, then go with a better cam. Factory grinds are pretty conservative.

Then get it all tuned, because the computer won't be very happy with you after the exhaust and cam changes.