The valve adjustment that you speak of is part of doing the head job. If you have a running problem because of this, the job was poorly done.

The adjustment made is only to the preloading of the hydraulic element. The only way this can cause a problem is if you are bottomed out and the valves aren't fully closing.

You probably have an airleak at the injector rail or the plug wires are a common problem. An experienced tech will not take long to ID either.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician