AuidiQ5$

It has a new intake manifold, so it should have vacuum, thanks for your advice!

S4'ed

The intake valve probably does not seal properly (the metal debris probably damaged the sealing surface), so during the exhaust stroke, hot exhaust gases leak past the intake valve, and then into the intake manifold, heating it up.

AuidiQ5$

Would a complete engine rebuild be a good recommedation or not

simplesez

You don't have compression on two cylinders and two spark plugs are gone. Pretty obvious you need a tear down. Or replace the engine. Been trying to tell you that. Surprised you tried to replace parts and run this engine. Probably going to blow up again if you drive it.

silver_tt

Possibly the intake valves have so much carbon build up (problem with DFI) that they did not seat properly. Agree with S4 in post #12. Ya you can rebuild the engine, that's what I would do. You should also choose a low volatility oil to prevent this problem in the future. Also a good idea to get one formulated to prevent LSPI. This motor is cheap and easy to rebuild......