[Thursday23]

A leak-down test should let you know if you have at minimum bent valves.

Oil level/condition not being the same as oil pressure, you could still have some oil starvation up top in valve train.

Of course, very possible to 'float' a valve on a missed shift as well.

Depending on how recent the head gasket work was, might be worth verifying timing isn't off. Technicians can be reluctant to admit mistakes at times. Lining the cams up to the wrong mark(s) when reinstalling the timing belt after head work is not impossible.

And add to that, if the head work did require re-surfacing/decking the head, the clearance between the valves and pistons is reduced, a very small amount for sure, but reduced all the same. Add to that either an over-rev or a timing error, plus valve spring which could be a little fatigued, very possible you start bending valves.

But, to answer your question, if a valve did bend due to over-rev you could possibly get a misfire code p03xx, if you have the ability to also check the freezedata when it set, you might see elevated engine speed. Typically the misifre wouldn't trigger at the first misfire detection, but you might still see a 7000+ rpm with a vehicle speed of 50-60mph (the typical missed 5-4 shift speed) through a few subsequent triggers.

Since it sounds like you have a horse in the race on this one, if your leak down test confirms a bent valve, and you've confirmed timing is still on, I'd explore a possible overrev.