I mounted my MBRP, completed Cobb S3 process, could not take the drone at fast cruise so switched back to OEM exhaust. Logs showed absolutely no difference between exhaust systems in performance on Cobb S3 V201.
I later revised MBRP to Vibrant resonator and muffler, all 3" straight through, added a vibration damper off an old Mercury Maquis my local shop gave me out of trash, it actually worked to reduce drone. But this is in prep for Cyborg mount, otherwise I would have stayed with stock exhaust. When I revised to S3 V220 I picked up a few hp.
No idea whether exhaust makes any difference, doubt it, but I drive the car better with more auditory feedback than stock provides. Course my hearing is poor, too many loud experiences in my past maybe. Wearing helmet its much easier to drive than stock exhaust, so I am keeping it for tracking. No need to view tach is very useful on track.
As long as I ease around town its reasonably stealthy. And it looks very plain and muffled.