What makes you so negative about the Pierburg units from ECP Kev? I know ECP are shocking but I don't see whats wrong with parts literally the same as OE. I got a Pierburg throttle flap off them the other day for a Audi which even had the VAG part number cast in it.

Back to the topic you can clean them by unbolting the solenoid from the valve. You'll find the pin that the solenoid acts on sticks in - it should normally spring in and out. A bit of a clean and lubricate gets them working again.

Matt