1.9dg stalls when warm will not restart intermittant

[sandfish]

hi all, i'm a bit new to the 1.9 dg ( i am looking after this one for a friend) here is the problem,

van starts very well just about all the time, has had a full survice in last 150 miles, recently it has developed an intermitant fault in that when driving for more then 20 mins or so it may cut out, and will not restart untill cold,
I thought i had it sussed as the coil was over heating (as in hot not just warm) and when tested the values were wrong, I also found a piece of red plastic in the carb fuel filter (strange as it was ridged and about 10mm long)

however it has done it again, stalled when driving as if it had been switched off, will not restart till cold, i have tested every thing i can think of i.e. fuel cut off, coil, hall sender and all seem to be ok , although i cant get it to do it when its on the drive !!!

any thoughts ???

thanks martin

[Evsi]

Do these have an ignition amplifier? Used to have a problem with them on the older vw's.