Hi im new to the forum. i have a 1990 pontiac firebird formula 305 TBI. currently i have the stock headers but i want to convert my y pipe to an x pipe. has anyone done this? or does anyone have any thoughts for a complete new exhaust?

 

I think you're looking at two different animals here. The X pipe deal, like an H pipe, is for full length dual exhaust systems. Your car has two down pipes from the engine into one larger pipe to the rear. Best improvement would be with tube headers, high flow cat. converter, and a cat back exhaust system. Whole lot of money and real aggravating work to get this all done. Not sure the 305 powerplant is worth the difficulty unless you are doing a complete car rebuild.