Is muffler pressure needed on an OS .70 Surpass? I obtained one from a friend that used a flex pipe that promptly cracked after a few flights. I want to fly with this but wonder if the engine will lean out too much without muffler pressure. I've run the engine with a straight pipe on the ground and tehre doesn't seem to be any problems.Thereseems to be little if any difference in sound without the muffler attatched to the flex pipe.

bhady</p>