Nope, no problems with the exhaust valve open. Many other vehicles with much louder setups. Don't have any dyno numbers, might have to get that from Full Race themselves. I imagine the gains will be similar to many of the other exhaust systems out there which some of them are documented.So, misterchonger, did you get any grief at the auto-x? Also, do you or anyone else have any before/after dyno numbers for this system? It looks nice and sounds cool, but I would like to know what performance advantage I might expect before I consider purchasing an exhaust system.