The electrical connector and vacuum pipe on the TDI cars is to operate a butterfly flap in the airbox, over about 3K RPM this will open to admit more air.
You could block the vacuum pipe and disconnect the solenoid from the air box and connect it to the connector. This will stop you getting an error code as the ECU will see the solenoid as open circuit.
If you look at the build thread for my car there are some pictures of the solenoid and flap in the airbox. I can't believe that the change of air filter is worth 13.5 bhp though.