Benm, how'd you go with your mechanic? ive had this problem for a long while, but my car doesn't idle at all... not just every now and then.... very annoying!
had a look into the fuel pump connections.. there are 2 plugs
one with 2 wires, and one with 3 wires...
my guess that the 3 wire plug is for the fuel level sender attached to the fuel pump assembly +ve -ve and sender wire..
if thats right then the 2 wire plug is the one we need and i would say it is the black wire! havent looked into it too much more but i will get the multimeter out tomorrow and check it out, and mod it to see!