I have a sohc d15b turbo eg,now recently it started getting blow by(my fuel pressure regulator and gauge crapped out so im guessing it ran lean)

Now i know blow by is mostly a cause of bad rings,but id rather be 100 percent sure before i yank the damn thing out.

So i did a compression test today from cyl.1-4 i had 170,165,165,then 65

So as you can tell cylinder 4 just about had all it could handle,now i am trying to decide if whether i burent up the valves on the cylinder,causing a loss in compression and oil to seep through and get burent off of the piston dome,or if indeed my rings are blown out.

Any opinions are appreciated,id much rather just swap another head on the thing than yank the motor.