LT4 Swapped Nova 8L problems

So we have inherited another shops job. Lt4/8L90 installed in 66' Nova with speartech harness. The PCM and TCM were flashed by Speartech with correct OSs. The shop couldnt get the car to shift so they condemned his A8 and sent him on his way. We installed a 2018 8L (Had '19 8L90 installed) and it went through the gears fine. Fast forward 2 months and he wants a Speartech TUTD shifter, ok. Installed it yesterday. Now its as if trans is in Limp Mode. Has little to no throttle response and doesnt even seem to load up at all when put into drive. So i put VCM scanner on it, no codes, everything normal, but when i watch PRNDL status it goes Park > Rev > Neutral > Unknown 82 >Unknown 81. I have verified TUTD is enabled and this TCM is set as a '15 Vette. Do i just have a faulty shifter? Is there more setup than previously anticipated?

What year model is the ECM?

You ever get it fixed?

I believe you need to delete codes that no the TCM side if things for tutd to work properly on a swap tune. PM me if you want to look over my tune and see what codes i messed with

I have had limp mode issues with the transmissions as well. It will go instantly to limp mode when a can bus module is installed. It?s a complex fix. Speartech should be aware of the issue. What did they say? My muscle car module was doing it to 2018 and newer transmissions. Basically the transmission would act like it was in neutral.