I have an OS95AX with a pretty bad vibration at lower RPMs. When it's close to idle speed, the vibrations are very noticeable, especially around the vertical stabalizer. But at any from mid range to wide open throttle, the vibrations are no longer present. I've already checked all the screws/bolts on the mount and firewall and everything is tight. I've also tried a few different props and I also balance all my props. Any thoughts?

The other thing I've noticed is that if I spin the prop in reverse (clockwise when looking from the front), at the compression point but before it turns over there is a slight metalic click or pinging like sound. Is this normal?