Standalone TCU problem with LS3

I have here a 60's Impala with crate LS3 and P2138 error code on as soon as the pedal is moved. I disconnected EC-TCU which is controlling the transmission and got rid of the code and the car drives again (with "limp mode"). I assume the TPS signal is splitted for the TCU also and now it's doing something wrong in between.

Tune says it's manual trans. PCM is E67. Is the automatic transmission software it "built in" the ecu and could be activated if the EC-TCU will be discarded? All 3 connectors in PCM are in use and I thought one of those would have been for automatic tranny.

The tune and log attached. In that log the T/B problem was present and I cleared codes few times to rev it.