I fly an avistar with a tower 46 pro. The other day I was flying and when I brought the plane in for a landing I noticed the muffler bolts had loosened up. I also noticed that the plane ran better with the muffler loose. Tha rpm's went up on full throttle, and it ran smoother. why did this happen. I did tighten the bolts back up and continued to fly but, why would the engine gain rpm's and sound better with a loose muffler.