I got a T3 Summum with dual end pipes and installing the R-Design diffusor was easy. End pipes are just fastened by clips that slide in place behind the thick end of the exhaust. About half a hour did it take for me to just swap everything.
I fitted the diffuser with the instructions provided on the previous post. Was pretty easy job. Just 2 screws and carefully untucking the old diffuser from the bumper.
The tailpipes looked very small after changing the diffuser. I had a muffler delete and fitted 4" tail pipes.