Evap? PCV? Gremlins?

[RICHARDSMINI]

Strange but True!!! Our 04 mini died on the road a while back. Diagnosed a bad fuel pump. Replaced that and filter. All fine. Drive it for a few days and it drives great BUT dies again while driving. Here's the weird part.
For some reason when we take off the gas cap, it will restart. Happened again today. Mechanic said we do have a small leak in an evap hose but it probably shouldn't cause it to die.
So, I take off the gas cap, wipe it out, wiggle around the gasket and it restarts right away. Has anyone heard these same strange tales? Someone suggested it could be a clogged PCV causing a pressure build which is relieved when I take off the gas cap.
cheers
RKL