I am running a FloPro dual 2.5" in and single 2.5" out 14" muffler before my turbo. It is a chambered design. I did not find it too poppy or too much drone I just found it too loud. The muffler did a good job of tonning it down but my wife still complains about it so it is really not all that guiet but it does not drone. I did a before and after G-Tech run and gained about a tenth so it does not seem to be hurting performance at the 10 psi I am running.