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I said they will pass unless something is seriously wrong.
If he failed, and a valve adjustment fixed it, he was badly in need of that service. Tight valves cause compression loss. The diesel purge probably cleaned up the nozzles so the spray pattern was better, and driving like you stole it loads up the engine and the higher temps burn excess Carbon out of the prechamber. That's why he passed the second time.
If you do the valve adjustment for the first time, make sure to set them correctly and then drive it hard for 500 miles. Then do another adjustment and seal it up for 15k miles. If it's been a while, Carbon builds up where the valve margin is supposed to sit on the seat. After your initial adjust, the crud will wear away and the valves will need to be adjusted again. After the second one, you'll be set.
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