Runs great 4 about 20 miles then starts 2 Stutter

[GTI EDITION (aka LTD)]

Is changing the filler neck as easy as it looks?

In a word YES , as long as the 3 screws undo ( behind the black circular sticker around the inlet where it fits to the body, you may need a new one as they are stuck on ) , and also the 2 jubilee clips undo .
 P.S.   If you run it low on fuel then jack it up the tank shouldn't need draining down.

  P.P.S.     OBVIOUSLY.... MAKE SURE NOBODYS SMOKING WHEN YOU DO IT !! ( thought I should just say that )

[gbmgbm1]

Any idea how easy or hard the tank is to remove and give a good clean out?

[GTI EDITION (aka LTD)]

It's not a bad job getting the tank out but the problem is getting it cleaned out as you cannot easily flush it out even when it is removed.
 You may need to take it to a specialist to get it cleaned ( a car radiator refurb/specialist look in the Yellow Pages, give them a call to see whether they do tank cleaning, As it maybe cheaper to get a new tank in the end.

[Danny]

Does anyone think it could be a Vacuum problem?

[carrie]

this may sound weird but try the fuel cap (i am serious).
this can happen, a car which is suppoed to have a vented cap gets one which isnt or the vent get blocked/ dont work then vacuum builds up in the tank the pump can overcome it and the car seems like it has run out of petrol, later it will start due to air leaking in / fuel vapour filling the void and all is ok then it happens again.
worth a go and not too expensive. i have heard of this happening and people replacing loads of bits on the car then finding this is the cause