subymamma et al:
The sound in the cabin is quiet...just a nice v-8 and/or v-twin rumble (reminds me a lil' of my Ducati). I find myself opening the roof so I can hear it and it sounds sweet. I switched from stromung and didn't note any power loss (butt-dyno mind you!). Gas mileage is good although my car has been problematic (ce light) and diagnostics are now squared away (awaiting installation of new cats under warranty).