Got a torque converter question.

Just got through doing a 5.3 to 6.2 swap on my 13 Silverado. Figured while I had it apart I would upgrade my converter from the stock one. After doing some research I landed on the TC0017 converter from luk. I know, a billit one would be better but this was a budget build for me. Got it all put in today and fired up. Everything has gone well except for the converter. It's not acting right. The truck will shift, but it's honestly acting like a bad converter would. Fluctuating rpm's, doesn't shift on time, etc. Honestly at a loss, don't know what would cause this. I put 2 quarts in it and spun it around on the floor before installing it, let the truck idle for about 10 mins to let it fill up before I drove it. One thing I keep going back to is maybe it's electronic? The engine I got came out of a 2011 Yukon and I got the ecm with it. All I did was unplug the original one and install this one and didn't tune anything. Could that have anything to do with it? Thanks in advance for the ideas and suggestions.