I stick by my comment about the tone being deeper if you put the complete Fabspeed setup on a stock car. It howls.... The tone definately has a few db of extra lows. No doubt. Obviously not as much as swapping mufflers, but there is more bottom.
2009 Space Gray Carbon Leather E90 with DCT, Tech package, and EPS. Mods: Fabspeed 200 cell cats, Xpipe w/resonators and no secondary cats, BPM tune, Euro DCT software, Eisenmann Sport Mufflers, Vorsteiner Rear Diffuser II, SWS8 subs, JL Audio XD400 bridged 2X200W, built in radar