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I assume you're talking about code P0302. If so, it will stay off after erased with a scan tool as long as the condition that caused it has been repaired.
A misfire code will set when the ECM detects the crank slows down as it's being rotated by a particular cylinder. This could be caused by several things, not just a bad injector. That, plus the puff of smoke makes me wonder if there is something more involved, like valves. Can your scan tool do balance tests? If so, could you share the results?
Yes, that's what I mentioned valves as being a potential problem. Without the proper scan tool, things get much harder to diagnose, but not impossible. Can you do a cylinder leak-down test? (much easier than a compression test)
Then it looks like the compression test is your only alternative. Remember, you're not looking so much for an exact pressure, but for a big discrepancy as compared to the other cylinders.
I'm about to log out for the day. Please post the results and I'll check on them as soon as I log back in at 2 PM EST.
I just reread your post about how it had happened when you were on Holiday - that really stinks...