I swapped a 09 engine and transmission into my 06.
What do you mean low power mode? Do you mean the car goes into limp mode? I'm guessing that you changed the transmission oil. We'll you'd have to drain it in order to get to the connector. Did you put in enough? What about the main connector, was it plug in properly? You'd have to to give more info on what you did with the swap in order to figure out what 8s going on. Does the car give any codes?