FWIW, spraying carb cleaner "all over the place", doesn't work for me either.

Instead, I have to get the spray tube way down in-between the intake and exhaust manifolds at the base of the stud very close (like up against) the manifold. Can't get to the bottom studs but the top, front and rear are easy to get that spray tube in real close. Usually have the engine running around 1200 rpm and it will drop 300 rpm or so when spraying and then pick up again after stopping spraying.

I don't know, your symptoms still sound exactly like what I have dealt with on mine.
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"Differences of opinions should be tolerated, but not if they're too different' - Sharon Craig