Which x pipe?

[Gunny]

Originally Posted by 32valvesftw

I have the same exhaust as you, the Borla Challenge, and also cut out the resonator and replaced with an X-Pipe. My drone increased dramatically. I don't know what brand of X-pipe it was. There was a seat of the pants power increase though.

I've had the regular Borla as well as the Borla Challenge and both had a pleasing sound for my taste (likes/dislikes of exhaust sound is highly subjective). As Russ mentioned the Borla resonator is somewhat restrictive and adding an X-pipe should be an ideal solution. But you will still have some (maybe more) resonance (drone). Try stuffing a shop rag in one outlet each side. I did this years ago (before anyone figured out about flappers on one outlet) and it cured the resonance ... I wanted to add a flapper but didn't know how nor who to ask.

Since I couldn't figure out a solution for the Borlas I eventually went to a stock LT4 exhaust (balance pipe behind the resonator) with long tube headers & no cats. Reasonably quiet with absolutely no resonance. I also added electric cutouts just before each muffler. The sound is incredible when wide open and, yes, there's plenty of resonance. But you can do a partial open on the cutouts and get some extra sound with barely perceptible resonance. There's a write up on the forums if you're interested - use the search engine. I think Haibeck installed the electric cutouts on Bob's polo green.