Well I would find out whats wrong with your car before you just start changing things and not having it fix the problem. Obviously if your exhaust manifold and y-pipe are broken than fixing it would be a good thing, but if there are other things wrong with it nows a good time to fix it. Are you throwing codes? And if so have you even checked them? Checking your codes wont hurt anything. You could find out that it isnt even related to your o2 sensor.

 

I fully agree with grimmcs here, but I wanted to add something, good luck finding new manifolds for a reasonable price. You can always find them in the junk yard, but they're always rusty on the outside, and corroded on the inside--and very brittle mind you. I'd recommend getting a set of headers, they may cost like $300 or a little less for the cheapest ones, but they're made of steel, not cast iron (which corrodes and rusts like mad on thin walled things like manifolds at high temps. They'll last longer and may add a little bit of power, on a 2.8 it might be unnoticeable, but I think it's worth the upgrade. I'd recommend at least putting some insulating material on them though, you want to keep your exhaust hot and the engine compartment cool.

 

First Firebird has a set he's delivering to my parents in Florida. If there's on cracks on those, I'll mig them shut, and grind it smooth. Plus, at school I have access to 10X as many tools as I do here, sandblaster, mig, arc, stuff like that. I can't afford headers either, I just lost my job so It's gonna be bare minimum for a long time. Thanks KP.

 

An exhaust leak can definately interfere with your O2 readings. Nothing's wrong with junkyard parts as long as you grab decent parts to start with. Just beadblast 'em and spray them with some high temp header paint. Same with the y-pipe.

 

Thanks man, This is the cheapest route I could think of. If it was MAF, it would've changed because I cleaned that bugger so well. Plus thats expensive..