My 1996 Feroza makes a droning/vibration noise around 2700 rpm. Below or above these revs the noise dissapears. It appears to come from the left hand side rear of the engine and first impressions are a loose protector plate on the muffler pipes. Not so. All plastics on the air cleaner and associated hardware also checked for loose screws. Nothing! Has anyone else experienced this or have any clues where else I can look. Its more frustrating (I hope) than any potential problem.