Hi Brian; The gentleman who designed the first ones has them in a Lanier Staudacer, BME 105 powered. He has been flying IMAC with his setup most of the summer. There is a pic of his instalation in my gallery. So far they have been holding up very well, Only flying time will tell.
The sound level on my 46cc Poulan is in the mid to high 80db range with a 200 to 500 rpm drop from an open header. I keep playing around modifying things. I regret to say I have yet to get a flying combo together for the Poulan due to to many other projects going on this summer so I have had to rely on other guys flying for any muffler testing.
Adam