ORIGINAL: Lowlevlflyer
Another bit of info for you... a bunch of people say that the OS 1.60FX wont run well with a Pitts muffler unless you crimp one of the stacks closed, because the muffler wont develop enough back pressure. I would suggest running your engine first and see how it does. I lost count of how many guys told me mine would never run right with both stacks of my Brison muffler open, but it has run like a charm since the first day I installed it, with no back pressure problems.