Like joe says...make sure the pipe IS and STAYS seated in the cylinder. If you unseat the pipe in the process of yanking around the mounting tabs to force a bad-fit issue, you're going to have an exhaust leak that will ruin the performance of the bike.
Seems FMF is famous for lousy fit&finish. My brand new pipe had a hole in the stinger weld for example. Their advice, 'fix it yourself'.
If it's off far enough to cause a problem with the cylinder fit, take it/send it back to wherever it came from and get another one.
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- OLD member
'oh-oh' KDX 200
'86 Nighthawk 700 SC
(a motorcyle even if it doesn't have a chain!)