Before I put a pre-tuned pipe on mine (46FX), it would scoot pretty good even though the RPM's weren't all that great. I have been running an 11x6 just to keep the speed down. While I personally was considering putting a Saito 72 on my Aresti, I think I'll just put it on a fun-fly instead. The Aresti is pretty quick on the 46FX without a tuned pipe. I'll let you know what the Tower muffler does next time I take it up.