One thing ive noticed is condensation in my oil catch can and lines. I assume this only happens during warm up and dries out as the engine get hotter.
So far i have about 2 inches of water in my catch can, with about 5mm of oil sitting on top. Its a pretty good indicator to see how much the engine breathes (not much )
Ill be pulling the can out in the next service to have a look see.
Also a friend of mine has just turned key on a big RB 2530 engine (on E85) The exhaust is all new too and we can see very light surface rust inside the tip. No carbon though