I run my Saito 91 on homemade straight pipe about 5" long with one 90 degree bend about 1-1/2" from engine exhaust port, no muffler pressure, runs great and sounds good, but its not any louder than stock muffler. Just use the fitting that comes with engine for muffler and braze on a short piece of copper tubing (K & S brass tubing will crack under vibration). Try it, you will like the sound and how the engine runs.