I had the same problem with my mk2 16v! when ibought the car it had had a new fuel pump, and i was lucky enough to have a spare car sitting in the garden in good mechanical order! I changed all parts you could think of to do with ignition and so on, fuel regulator, but the car still cut out when warmed up without any notice once across a duel carrige way with vehicles approaching in rush hour traffic, felt really embarassed to have to push a mint mk2 away, but i was lucky no one had crashed into the mk2! And on the way to inters the car was fine until we had to wait to pay and get in no sooner had we gone through and you had a bit of a run to park up and she died again! Any way in the end when i changed the fuel lift pump in the fuel tank problem solved!! Some one did mention this before, any she doesn't miss a beat now!!!!