you may also wanna check the cable adjustments on the choke to make sure when you have it off, it is really off, and also make sure that the throttle isnt too tight. But to be honest, the idle issue sounds like they messed up shimming or something.
also the popping is somewhat normal. before your carbs were gunked some. so at idle and decel, you run lean, so no pop, but now it may run a lil rich (which is normal).
i suggest a normal check out on the carbs. this includes seafoam, syncing, draining the bowls, check the boots (yes makes a difference), check the cable adjustments, after all that, then adjust the idle. also i would check the air filters, when was the last time they were cleaned? I am in dallas and drive by construction, so i clean mine every 6-9k miles.
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