How much HP can I realistically gain from headers on this car? It has a 2-3 year old Magnaflow cat and 3" catback the previous owner installed, a Hypertech Stage 2 chip (yes, I know they suck, but it came with the car and its better than OEM...), and a 14x3 open element air cleaner. Short of POSSIBLY doing an Edelbrock TBI intake manifold, my engine mod plans are pretty much complete. Someday if/when the motor gives up (I drive it 4-5k miles per year, so that won't be for a long, long time), I will probably do Vortec heads and an LT1 cam...

Will headers make a real difference with this basic of a setup? How much louder will the car be? Will I at least have achieved close to 200hp with the above setup? Thanks to anyone who can help...at least I can say the recent open element install made a difference!!!

 

Heres a real quick video I made from a 20mph roll to 70mph with the same mods that you want but its an automatic.
YouTube - 91 Camaro tbi

 

According to my timeslip I did 0-84 in 8.5 seconds and 84-106 in 4.7 seconds

 

Check my sig. SLP 1 3/4" headers & dual cats were worth less than 10 hp. On these cars, you're not going to see any real difference from basic "hot rod" mods unless you learn to tune it.

 

I can agree with that.

This is my 8.8:1 350, peanut cam, 1.6:1 rockers, stock heads, edelbrock intake, headers, exhaust, prom tuning, Yank 2,800, 700r4 with 4,800 rpm shifts, 3.73 gears, and P295/50/R17 tires. This is a 5,300 lbs G-Van. According to my timeslips I am running 0-67 MPH in 10.5 seconds and 1/8 mile. It will hit a 15.8 @ 86 mph in the 1/4. They started my dyno pull at 3,600 rpm, at 3,700 it was still making 261 RWTQ, it went on to make 177 RWHP @ 4,200 rpm. It should have been close to 300 RWTQ @ 2,400 rpm.

YouTube - Chevy Van 350 1

My more stockish 350 TBI in my 1991 went 11.41 @ 60 mph in the 1/8 and 17.9 @ 77 in the 1/4. This one is stock 350 TBI, 9.3:1 compression, stock hydraulic flat tappet cam, high flow cat, stock intake, stock heads, prom tuning, with stock 1,800 rpm converter in the 700r4, and stock 3.42:1 gears.

 

Well my car made the world of a difference with the hedman headers and only a 2 1/2 inch dynomax catback.