RE: AP Yello Jacket .15
I found that Blaisdell makes a felt tipped marker with a heavy aluminum boss on the end usually covered by a plastic cap that is just the right size to thread for the exhaust of the AP. I drilled thru the center of the boss and dug the innards out of the marker. I then pulled the felt tip out of the ferrule leaving a stinger. The stinger was slightly too large so I used an expandable collet and crimped it down to an appropriate size. The result is a pipe resembling a tuned pipe. It is not as quiet as the std muffler but it has little restriction. It is too short for any more than a 1/4 wave tuned exhaust.
I altered one with a sleeve in the center to allow the stinger end to slide out a way. The results were inconclusive as I was trying to tach rpm under florescent lights. I was drawn away by interest in other projects before completeing the tests.
blaisdell liquid tip 1100