I've been battling my XF350's for a while now. found the solution. If you own these, keep a few sets of these in your inventory. They cast $3.50. OMG all problems gone. I bought 6 sets . Its both the motor block inserts & bushings plus the cage bushing(long Prop). Unbelievable, all problems gone.
Maxspect Gyre Motor Block & Cage Bushings
A pair of Drive Bushing assembly (2 rubber boots-2 Ceramic inner bushing) for the Maxspect Gyre Generator pump.
www.coralvue.com