So it appears that the problem has been found. It appears that the Hyde soft mount (which is 5 plus years old with an unknown number of flights is bad). I made a temporary solid mount to try it without the soft mount and the problem was gone. I did inspect the "firewall" mounting and everything is stiff and still glued solidly to the fuse sides. The rear support is also solid and fits very snug around the aft end of the motor assembly. I am just going to make another mount for it and move one. This was pretty frustrating but at least I know the motor and gear box are good to go!