Solid mounts are miserable; If you want something more rigid look at the pre89 mounts. Harmonics breaking the surface tension isn't an issue anyone I know of has ever gone through in one of these engines (definitely not at power levels like you're seeing); You're grasping at a straw that isn't there. It's not worth the stress on the frame as it's not going to fix anything.
You sure there wasn't still crap from that blockage in the head stuck in there and waiting like a timebomb? You did miss it the first time. Could have been debris got stuck in the oil cooler too; Did you flush it?
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