RE: At a certain engine RPM my radio gear goes nuts ? Troubleshoot..
All of the above are valid suggestions. In addition you should look for any metal to metal connections that could resonate when your engine reaches certain RPM. I had a plane years ago that would do a snap roll occasionally for no apparent reason. A friend found the metal pushrod to the throttle would contact the crankcase at close to full throttle - slipped a piece of fuel tubing over it and the problem went away!
Phil