Mille SV engine, all mods done and had a dyno setup done on the PC3, ridden about six times since then was perfect after the dyno and a lot better (managed 124.9 BHP at the wheel)

Rode it the other day and its got an hesitation/ misfire around 3750 RPM, fine before and clears about 4000 RPM. Also it occasionally sounds like its spitting back through the throttle bodies. I have changed nothing since the dyno, checked plug leads and re-plugged a whole bunch of connectors, stumped

Any ideas chaps?