Maybe I've had a faulty BPC all along? :roll: Should there be a free passage of air through ALL 3 connections with it off the car? Mine is free between the turbo outlet and actuator but the return connector is blocked. It switches to the reverse of this when 12v is applied and stays there until the current is applied to the opposite pin where it switches back. I'm now suspicious that the default position is in the middle (all open) so that the air pressure from the turbo outlet is part fed to the actuator and part bled away. The ECU controls boost by modulating this path and thus can avoid the on/off boost that used to happen with the old APC systems on c900/9k cars and to which my car seems to be suffering.