i just swapped my burnt up 4l60 for a diff trans. Condition of replacement trans was unknow, so I decided to put a shift kit in it and run with it to see what would happen. When I pulled the pan off I found brand new parts inside, and a shift kit install already. So put the pan back on and installed it. After install the car now idles at 2800-3400 rpm. I did find a vaccum leak at the map sensor. Reinstalled the vacuum line and no change. After running for a bit, the drivers side header was glowing red. I still found no vacuum leaks. I am wondering if there is a chance that the trans could be causing this. I wouldn't think it would but I'm lost.