Well I've never heard of all poly mounts causing anything like that, although I've never tried it either. I run front and mid-motor plates with a poly trans mount and have never had a problem with that. I don't know what would have caused it but, I would think that case is garbage now
It broke behind the front pump, even the sealing surface for the pumps O-ring is gone! An Ultra bell bolts to the front of the front pump.