Crankcase blowby?

Is there any way in addition to worn rings that would force exhaust into the crankcase? I've got exhaust coming out the dipstick in a Saab 900 Turbo, but the compression turned out to be pretty healthy and mostly even (one cyl. down 12%). Car has a funky idle, too (slow rise from 1100 to 1600-ish, then fall, repeat), but don't know if that might be related (I have ruled out all of the usual idle suspects, e.g., vac. leaks, idle valve, etc.). Except for the idle, engine runs well. PCV valve works fine. Headgasket R&R 3k ago.

Thx...

crack between a cylinder and oil drain?

we had a lawnmower with a bent valve idle similar to that, but it would surge at nearly full throttle as well. possibly bent valve along with leaky seal? these are just my wild guesses, fairly likely cause is bad rings or cracked ring land/general bad sealing ring. iunno really without being there