Did you happen to check the fuel return line (and if your car has a valve at the tank, may want to make sure it's ok and air blows freely one direction, (back into the tank from regukator).
Yep.This seems like the only possibility left apart from a faulty FD.
So in order to check this, is it right that I take off the fuel return line from the back of the FPReg and blow into it (after depressurising the fuel system)?
Maybe the fuel is return to the tank at a certain pressure, which would explain why there's "resistance" when you blow into it even after changing the tank valve.Just a thought.
Anyway, it's coll that you're testing the fuel return line coz I'm dying to know of your results.
Let me know.
Thanks and good luck to you, too.