Did a test with the stock muffler, no spooge and that was after 20 min of high and low speed test runs.
Took apart the FMF, the packing next to the holes (see the carpenters knife) were completely closed off by the packing. It was very dense, like "glued on" almost. Looked like 4 stroke packing, not the 2 stroke packing that I just bought, which is less dense and more "fluffy" looking. See pics. So maybe every 40 hours or so pack your muff. OR repack it. You know what I mean...