Muffler is off. No catalyst to be found, just an expansion chamber. Exhaust port looks good, and the gasket doesn't look to cause any interference, matched up pretty good. So the actual exhaust port on the muffler seems to be the only area to modify. The spark screen is large enough to allow a substatial enlargement of the port, but I'm not removing it unless that's the area to modify. It can't be that easy, can it? If so, what ID do I shoot for, or is this a trial and error thing.-- Removed the screen, couldn't quite get the calipers in there, but visually lined up to about .425" diam. I can cut-off the deflector and re-weld it on, just wondering what diam. to enlarge the hole to? Anyone ever tried this, and if so what did you do? Thanks, I love this sh*t!