Thanks!
Thanks for the lead on SCal Diesel guys! You saved me over a $1,000! Guy set me up with a Powertrain control module (PCM) for a great deal and was able to bench flash it so all the shop has to do is put it in. He drop shipped it to my service shop. Of course that means I didn't have to tow my truck to the GM dealer, pay them for diagnosis, or take the PCM to them to beg them (or pay them) to flash it.
My shop swears it's the PCM, so we'll see if they're right. I did a ton of searching for GM parts, PCMs, recyclers, etc with very little luck until I found this site. The best I found was about $800 plus shipping and it wasn't even flashed. Hopefully if someone else has a PCM issue on their Duramax 6.6 diesel in the future they will search Google or Yahoo like I did, then find this site, this thread or Guy at SCal Diesel 661-775-5620 socaldiesel.com. Thanks, guys!