would i gain if i added headers to my LG4? i have a 3 inch cat back but how much will the headers help?

If you don't replace the y-pipe and weeney cat as well, next to none.

If you do go with headers, 2-1/4" down-pipes to 3" y, to 3" cat, you can expect about a 15 HP gain. It will be noticable but not substantial. If you haven't done so already, the air cleaner needs fixing, because it is just as restrictive to the engine (if not more) than the terrible exhaust. Either a factory or home-made dual-snorkel will make a noticable difference.

Then you'll be restricted by the cam. Then heads (at least valve springs). Then ignition.

But, replacing the exhaust from ports to rear bumper is the right place to start.

okay, well i dont have the cash to do all that at once, i'd like 2 find a dual snorkle off a vette and i wanna good flowing cat, any suggestions?

I'd suggest an '86-'90 TPI single-cat application piece, such as a CTO-9118 from Summit. You'll have to modify the cat-back to fit it, but that's no big deal. And, modify your current y-pipe to fit the cat so if in the future you can get headers & y-pipe, it'll fit to the cat w/o modification.