I hope this is the right area for this one. I have a couple Tower Hobbies 75 engines.....one brand new, never run, the other is giving me fits, again. It will start, runs at high idle, transitions good to high speed, but when returning to idle it will continue to run at about 4500 rpm, will slow if i push in on the low speed screw. Additionally, are there any extensions to move the muffler away from the side of the aircraft, say 1/4 to 3/8 inch, that goes between muffler and head of the engine?

Thanks,

Clint