Originally Posted by Rick

disconnect all the pipes from the metering unit.

undo the 3 torx holding the metering head in place.

gently lift it off - there is a rubber seal - careful u dont damage it.

U will then see a little piston which the flap works on. It should move in and out under gravity (ie when u turn it upside down - it should be very free) Spray the thing in WD etc to get it nice and loose, and soak all the fuel channels with WD too - then screw back on and see what happens...