Cm2250 vacuum on coolant system?

[Waterloo]

Who did the delete? If it was not someone here, I would suspect that is part of the issue. As far as your symptoms, fretted liner is my best guess. Pressurize the coolant system to 20 psi, drop the oil pan, have someone bar the motor, you are looking for coolant on the cylinder walls. When barring the motor, if you are in a quiet location, you will more than likely hear water gurgling up in the head. Normally the #5 cylinder is the place to start. Sounds like in frame time. And again, who programed the motor?