Obviously the majority of the gain from an O/R pipe is from removing the cats, but is there any noticable gain from just the 3" aftercat X?
I swapped out the factory h pipe with a basani true after cat x pipe and gained 7 hp...get one!
My testing also showed gains. The stock H pipe is 2.25". I went with the Ford X pipe which is 2.75" Should show even better gains with a supercharger.
Drag strip testing. Here's the thread but basically in 50 degree temps it went a best of 110.5mph and in 62 degree temps it went a best of 111.5mph
http://www.svtperformance.com/forums/2011-2014-mustangs-354/891861-ford-x-midpipe-installed.html
Proof?
So then no proof then.................Sure get 2 cars together 1 with and 1 without and then watch the x pipe car pull away!