Sorry to tell you, but it sounds like the dealership tech mis-diagnosed the problem.
They replaced the PCM, yet it could not cause the problems you mention (other than a no start), and usually a failed PCM will not damage a BCM.
The BCM if it fails can cause all the problems you mentioned, as well as a no start, since the BCM gives the OK to the PCM to allow the injectors to operate (part of the anti-theft feature, called PASSLOCK).
There is no ignition module. Therefore, I would bet the PCM was never at fault, and the BCM should have been replaced from day one.
Again, these are my thoughts, and it is hard to diagnose a problem when the problem is not in front of you.
However, all indications point to a technician who did something wrong.
I would demand that the dealer called the GM Warranty Parts Center (WPC) and tell them to get a BCM out to you...NOW.
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Black Sheep Hummer Squadron
(ME TOO)
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