heres something to check.

my old 340 used to coat the front dipstick area with oil after a high rpm run. anything about 6000 would do it easily. I would clean the motor, run around at relativily low rpms and id see nothing. make a blast up to 7000 and id see oil.

turns out I had broken 1 or 2 pistons right at the edges and was getting bad blowby. the blowby was coming out of the vent hole on the feule pump (theres a small vent hole on them near the top).

might want to check compression again and see if you have the same issue.

but another check to see if the pvc is working is to remove the breather and put a stiff piece of paper over the valve cover grommet. it should be sucked down onto the cover. if not, you have a restriction somewhere or really low vacuum.