Ok guys here's the lastest on my clylinder head. Nine days ago dealer decided #1 valves weren't closing, truck has been at dealer for 18 days. GM had dealer send heads out to be pressure tested, came back Friday as OK? I have since found out that diesel heads can't be pressure tested (told this from service mgr). GM and the dealer have decided to replace the head to see if this solves the miss. But still no answer from GM or the dealer on what cause the problem. Here's a number I've been rasing hell with GM customer service 866-966-9463. So far I gotten to the point which GM will extend my engine warranty to 150,000 if the repairs take care of the miss. Any more ideas. Thanks

Why do they say diesel heads can't be pressure tested? I hope they mean just duramax heads and not all diesel heads or they need to have a discussion with the machine shop that just tested the head on my Mercedes.

A clylinder miss would be easy to diag.
Injector,control of injector,compresson.
compression test and leakage test would isolate intake,exhaust or rings,head gsk.
the electrical circuit is common to have harness lose at the injector or the pass through at the valve cover.....

I doubt there is a head problem.....good luck....Patrick