I'm sorry about the mix-up. "M" motor was a VIN designation for a crate motors rated at 290 HP and very popular for GM usage. When I said paraphenolic oils it was referring to parafin based oils such as Quaker State, Pennsoil and some of the Castrol Entry level oils. I also had a thought about Teflon additives which should never be used during break-in running. It will give you the same fits as you are experiencing right now.