I mean if it was off, not incorrectly tensioned it would be running rough or not at all, right? I think I'm being paranoid but I think there's a little more vibration than there was before. I'm about to find one on craigslist and see if it vibrates and makes the same engine noise. As of right now she runs excellent. Secondly if its inproperly tensioed I run the risk of it failing. Could improper tension cause vibration?