Hi there everyone my first time posting here, sorry it’s such a long one!

Anyways I have a 1991 K2500 4x4 7.4L with 4l80e, I was having issues with the converter lock up and when you would let off the gas once you got back to it the truck would rev up like it was slipping then kick back down into gear and no torque converter lockup. I replaced the torque converter, TCC solenoid, filter and new fluid, my problem with the “slip like” issue is fixed and it shifts ok but for the first maybe 1 minute of driving it won’t shift into 3rd but once it shifts into 3rd the first time it shift flawlessly the rest of the time. After the torque converter install the truck starts good idles fine until you start changing gears, if I shift into reverse or drive the rpm drops to maybe 400-500 shift into park or neutral and the rpm shoots up to about 1400-1500 and stays there for a while (sometimes won’t come down) then I shift into gear and the rpm again goes all the way down to 500. The truck now will also stall at almost every light or stop sign and most times will stall once stopped after reversing. I am at a loss as to what the issue is, I suspect incorrect torque converter specs but I don’t know much about them or how much they can vary for a specific model of vehicle, the company I purchased from had me give them all the info on my vehicle so they could send the correct one. The truck has a new TPS, IACV, temp sensors, I can’t find any vacuum leaks or any forgotten plugs when re-installed. I’m at a complete loss on what the issue could be, I also want to say again these problems were not present until the new torque converter was installed. If anyone can help it would be much appreciated, thank you!