I'm buying two mufflers for dual exhaust (some of you may refer to them as "fart cans"). I am aware it is basically just straight piping the exhaust, but is there a way I can obtain some backpressure ... maybe by putting a reducer in the exhaust pipe before the muffler? AND WHAT SIZE is the pipe?? 2.5 inches? Input would be very much appreciated.. not so much opinions on rice burners though.