Ok so I have the summit brand headers pn G9005 and with a little searching the Doug's y pipe pn DOU-D901 supposedly fit according to reviews, surprisingly it does not, does anyone know of a header that fits that y pipe that's reasonably priced or a y pipe that fits the header? Thanks

 

That combo ain't gonna work.

Those Summit headers are basically Flowtech headers. Flowtech's Y-pipe might fit, might not. Probably not.

The Dougs headers the D901 goes with, are basically the Hooker 2460 headers.

Flowtechs are not great. The Hookers are a bit better, worst part about them is the Y-pipe that necks down to 2.5". Short of the Chinese Ebay headers, the Hooker 2460s are about the cheapest option that's not pure garbage. https://www.jegs.com/i/Hooker-Headers/520/2460/10002/-1

There is absolutely no 'standard' thirdgen header design. So as a general rule, you should never expect one brand header and another brand Y-pipe to work together. It's just dumb luck and outsourcing, stolen designs and so on that has resulted in Summit putting their brand name on a Flowtech product, and Dougs selling a remarkably similar header to the Hookers, that makes any mixing and matching remotely possible. For best results, buy headers that include the matching Y-pipe, or expect to make friends with an exhaust fabricator who can modify stuff to make it work.