Those photos are pretty wild. We all kind of take solid materials for granted. I'm glad it was just your manifold Cobred. Sucks to do double work, but nice to know it isn't your bottom end.
Intakes are tricky. I helped a friend sort out his rebuilt FE awhile back. It leaked like a sieve. FE's need not leak at all. A little RTV goes a long way properly applied.
We got it pretty much leak free and he was still losing a ton of
oil. I mean scary
oil loss... A quart every 50-60 miles or so. Yea. He wanted me to help him pull his engine and find the hole in the piston he "had" to have...
The plugs showed pretty heavy
oil build up but were not oil soaked, which surprized me with all the oil he was using, the car ran well... Too well to have serious problems with the rings, and the motor came from a reputable shop with less than 1,000 miles on it.
Long story short he didn't torque the intake as well as he should have. He did it once and never retorqued it. I like to torque in increments and I started his at 20 ft lbs. Each bolt went 1/2 turn. 25 lbs. 1/2 turn 30 lbs were a little less and 35 lbs were about 1/4 turn.
I wish I'd started lower to see where he was when we started. I'm guessing they were at 15 lbs. He swears they were 32 pounds when he installed the intake, maybe they were, maybe they weren't. It never hurts to retorque a bolt.
The result was immediate. No more oil usage.