As it warms up, the cracks open up.

I am having a similar issue. I seriously suspect the heads.

 

Did aluminum plenum plate repair along with a new double roller timing chain set. This has solved my original problems by 85 percent. Still has a bearable very slight miss at idle even though it's warmed up outside. 900 miles since repair and oil use is noticeably less/ 1/8 in on dipstick, compared to a quart in 1500 miles before new plenum plate..The gasket was in place and not blown out, but obviously oil was getting sucked past the brittle gasket. Some conclusion anyway for whoever may stumble on this thread. Keep turning to the right!