I'm running a mid pipe right now but is it possible to run a test pipe as well or is it either or? I did some searching and the test pipe replaces the cat but the mid pipe replaces both the cat and the resonator. Thanks!

 

Yeah, a test pipe usually is a straight-flowing portion of exhaust tubing that is put in place of a cat (maybe even a resonator); but you've already got that mid-pipe, so you're good.