Is it possible for the muffler to overheat?im running a tt39 engine with a zimmermann muffler, no probs with the temp of the engine, can touch the backplate after flight and it aint too hot.but the muffler seems to get very hot, is this normal?its actualy turnd very slightly brown, i think its fuel residue burnin onto the outside of it. think i might be runnin it too rich and that'd explain the residue everywhere. But if it is very rich then whys the muffler so hot