My dad has a 04 dodge cummins. When we got it we put a airraid intake on it. This past winter we put a bd performance chip in it. A couple weeks ago i was at a buddies house with it and decided to straight pipe. Now when we floor it and it downshifts with the chip turned up it sputters and sounds like it backfires. Would this be a injector issue? Thanks

I would start with a fuel filter.

fuel filter is new. I think the transmission might need some help to. or just get a built one.