bring everything over from one car to the other, which would be: ECU Wire harness Boost solenoids Front Aux Fan Fuel Pump controller Fuel Pump Controller Sub harness Fuel Pump And obviously everything else for the actual conversion, but those are the main electrical things that are connected to the ECU and will not work by using a NA ECU. There is also the matter of the TT cluster having a boost gauge, but most people run aftermarket anyways. I cant think of anything else at the moment, but those are the big ones that sometimes get overlooked when converting.