OK I have a 1992 Camaro with a 305TBI. It has the following on it: total rebuild + heads, edelbrock performer tbi intake manifold, comp cam, comp cam springs, custom made chip, 3in cat back exhaust, no cat or emissions crap, msd blaster coil, everything else in the ignition is also new, open element, 165f themostat. So the problem is if I should upgrade my stock exhaust manifolds and y-pipe to headers and a new larger y-pipe. My dad says I don't need too but I know for a fact I do. The engine simply can't breath and my dad dosen't see that, but I do. So I am asking someone to answer back but in serious terms so I can't print it off and show my dad that the L03 stock exhaust manifolds and y-pipe just plain suck.
Thanks alot guys,
Cory Mohr

 

I would think that an aftermarket free flowing exhaust would have been one of the first mods. It made a huge difference in my stock LO3.

 

My vans 305 came with a 3" after cat exhaust, better flowing 2 1/4" outlet manifolds, and 2 1/4" pipes before the Y. The output was over 10 HP/15ft/lbs better than a car L03. It still benifited greatly going from stock to headers and a full exhaust.

 

I recently replaced my complete exhaust. 1-5/8" headers, 3" collectors. And a 3" y-pipe. I dont have any technical info, but I can tell you to save your money on a pre-built y-pipe. Mine goes from two 3" pipes, to a single 2-1/2". I went to have the muffler welded, and the shop owner said he could have welded a complete 3" pipe for $100 less than what I paid for that one.

But, the headers are great, and really helped the car. I have an issue Im tracking down, but it still runs better. But, again it was a complete exhaust. My car had the 2-1/2" exhaust from the factory, and the y-pipe was bad. All the bends were crimped, and the y section where the one end went into the other, was a straight shot, 90 degrees. Not very effecient. All the new stuff is mandrel bent. And the fact that the headers are made of mandrel bent tubes, and not an actual manifold, is an argument in itself.