Randy, you ought to lock this thread as a way to stop the flow of misinformation.
Where did this $70 number come from? That shop must have a labor rate of $420 per hour, cause the update process only takes about 10 minutes at most.
Coils do NOT have to be kept with the carb. You load firmware into the carb based on which coil it has. The CST will not load firmware into anything unless you select a coil from the drop down window. If you mix and match you must do an update so the carb and coil are properly linked. Only exception to this rule are the earliest 555/562's with the EL44 carbs.
Some guy came in yesterday with a 550, and I have a feeling he's been reading this thread! He says, "I was reading online", (usually a bad start to any conversation), and he went in and screwed around with his bleed screw and the saw is all out of wack. Normally I do an update right there while the customer waits, but I made him leave the saw. If an update solves his problem then he gets out cheap, but if not he's up for a new AT12, cause I'm not gong to waste my time, or his money figuring out what he did.
AT doesn't "go lean", the default is to fail rich. Which is why a saw can live for a while with an air leak. I've seen this feature save some saws, but the downside is that it can hide an air leak that will eventually fry the saw. Ya can't work on these things without a mighty-vac. Block off plates are cheap. Saws with air leaks will have a failure code or 2. Can be deceiving as IMO running the saw dry can also generate code 13 or 17, then you do the vac test and it's tight as a drum.
Decos can pass the test on the bench, but then can show a slight leak when running. (spray a little soapy water on it while running). 10PSI from the mighty-vac vs 150+ while running. I don't know that this really means much. Just that there's a lot of pieces to these puzzles and they should all be looked at before drawing conclusions. But any deco leak on the mighty vac, and it's got to go.
I need breakfast.............