I just put on an emgo dunstall replica exhaust to quiet things down on my '73 cb350. I was hoping it would provide a little more back pressure than the completely open shorty mufflers it's replacing, but it doesn't. It's also a straight-through perforated baffle construction and the bike runs a bit lean I think. Giving WOT from idle or even blipping the throttle quickly from idle, it falls flat on its face at 5-6k rpm or can die outright. For those of you who have made more open aftermarket exhausts work, did you make any jetting modifications and if so, what is a good place for me to start? Should I step up both the primary/secondary mains? I am running the stock air filters and everything on the engine/ignition is in good order and set to spec.