How do you still maintain the npp function? From my understanding the super 10 is just an open chamber with like two arrow shaped baffles and that's it. Closing off one side would only make all the exhaust exit one pipe but that is in no way a different path or more restrictive path. Did you cut them open and chamber off the one side? I just dont see how that even works lol. Your car does sound really good tho!
http://www.flowmastermufflers.com/super-10-series/