Questions about aftermarket down pipe

[4azdmunky]

I’ve been looking at finishing up my exhaust system and have had the opportunity a couple of times to purchase JP midpipes. I already have a DC Sport Header and a Magnaflow cat back (although it is actually a after cat back). The stock down pipe with the stock cat are the parts I’m looking at replacing now. It looks like the I.D. of the outlet on the header is stock @ 1.8” (I think) , and obviously it bolts right up to the stock down pipe. Do any of the aftermarket exhaust systems replace this down pipe with bigger size? Would taking this to 2.5” be possible and still have it bolt up at the donut? I do have a SC installed, and the Magnaflow is 2.5”. Going to 2.5” all the way through should help, or would I lose too much back pressure?If the aftermarkets are the same size, then I’ll just replace the cat with a hi-flow.

[satur9]

jp midpipe is 2.25 the cat is farther back to prevent burnup(some stock cats have from the extra heat. and 1 resonator instead of 2.