318 valve seals, HELP!

I've been running Pennzoil synthetic 10W-30 in my 318 "P"-code in my
M-body for years now, and a peculiar problem has cropped up causing
excessive oil consumptionl. At around 90K, I replaced both intake and
exhaust valve seals with Fel-Pro kit SS70014, which is their "premium"
polyacrylate valve seal kit for just about every LA engine out there,
and all was well...maybe a half quart consumption in 3K miles and it
ran as new.

Suddenly, it started gulping oil at around a quart in 1K, the plugs
were becoming oil fouled and everything started going to crap. After
some investigation, I popped the valve covers and lo and behold, BOTH
intake and exhaust seals were swollen to the point of not even working
at all, and the exhaust umbrellas had loosened up and wound up right
underneath the retainers! I replaced them all again, and went back to
near-zero oil consumption, but it happened again! Bendix is useless
for consumer complaints, but I think it's the synthetic oil swelling
up these polyacrylate seals.

Anyway, I rummaged through my rollaround and found an old set of
Chrysler umbrellas for the exhausts that appeared to be Viton, and
stuck those on the exhaust while putting new polyacrylate on the
intakes...the problem with the exhaust seals went away, but the
intakes are swelling up again!

Anyone have a clue as to WTF's going on here? Surely, if these
Fel-Pro seals are having trouble with synthetic oil, SOMEONE must know
there's a big problem! I know one thing...I'm going to have to go to
reuseable rocker cover gaskets soon!