Howdy Everyone! This is my first post here, glad to see a group of people sharing knowledge! I've got a 2011 GMC Yukon Denali with the 6.2L and 6L80 transmission. I recently suffered a collapsed intake lifter on the #1 cylinder, but was able to get it freed up using the lifter release tool and sent the ECM out to LT1Swap.com to have it tuned to turn the DOD/AFM system off. While waiting for the ECM to return, I changed the plugs and wires and buttoned up the intake and everything else I had apart while freeing up the lifter. So on Monday my ECM arrived back to me, I was tickled to death to get my truck back on the road. I had the battery disconnected the entire time the unit was down, and swapped it out for a new one as well. So I plugged the ECM in, connected my battery, triple-checked all the wiring connections, and fired it up. The engine ran great, smooth idle, no immediate lights on the dash, no lifter ticking or engine misfiring, I'm in business!! So I thought... I pulled out of the driveway and started getting all the typical warnings on the dash "service stabilitrak", "service traction control", "service side blind zone alert system" and a check engine light. When I went to pull out onto the road it just didn't feel right, the engine was smooth, but it was like my transmission was slipping, bad! I noticed that the little indicator on the dash to let you know which gear you're in didn't move with the gear selector. I also noticed the trans temp was not being displayed like it usually did. I made a short trip, maybe half a mile, and came back home, livid! I looked over everything I had touched during the repairs and removed the fuse block cover under the hood. I noticed a missing fuse (fuse 14 (?) TCM Batt) that I'm still unsure how or why it was pulled, but it was, there was no fuse in that spot. I went ahead and popped a new 15 amp fuse in that spot, and tried it again, no more lights or warnings! The cluster showed the gear indicator position and trans temp. I'm still unsure how that fuse was pulled, as I did all the work myself, in my driveway, and I know I didn't remove any fuses, but either way, it is what it is... I went for another test drive and the engine runs smooth and no issues there, no warnings or lights on the dash, but the transmission is still acting up. Once I get going, it seems to do okay, but if I get stopped at a red light, I can't take back off again. I have to baby the throttle very gently to get it to slowly start to move the truck. I flushed the transmission and cooler, and replaced the trans filter, earlier this summer before a long road trip. I've never had any transmission issues with this truck, ever. I babied it a couple miles home when the lifter collapsed and it was fine then. I went down a rabbit hole on the interwebs and YouTube looking for a resolution. I ended up dropping the transmission pan, pulling the TECHM/Valve Body assembly, and looking for any issues I could find. All checked out okay, no metal in the pan or anywhere else, the screens on the TECHM were clear, all the check balls were where they're supposed to be and not hung up. I put it all back together, filled it with fluids, went for another drive and still the exact same issue. I emailed the guy at LT1Swap.com and he's remained solid in that it's nothing he did. He says he's performed this same tuning on thousands of trucks without issue. So now I'm stuck, don't know what to do. I've read that there's a "relearning" procedure for the transmission adapts, but I don't have the diagnostic tooling to do that myself. I'm currently trying to find a shop that has the capabilities, and will want to fool with this thing after all I've been through with it thus far. My gut tells me that it's not a mechanical issue, but something with the tuning, as the engine ECM and trans TCM are very closely related in their operation. I just don't know what my next steps should look like. Any help or advice is greatly appreciated!!