I did a swap recently of a ucf20 ls400 ecu to celsior. Video here
It resulted in the egr being turned off without codes and a code behind for hydraulic fan. Car ran fine and code didnt result in check light.
Have you not got a good ECU rebuilder you can use? I would be happy enough to swap to a celsior ecu however I have the advantage of trying one first as I keep a test ecu from each ecu range. Cheers.