Hi,
I recently bought a mk2 16 valver and it does the same but it only does it when the engine is warm. The guy who owned it before me (i reckon) has taken out the thermostat as the fan doesn't work which means the engine never gets to full temp and the cutting out never happens, but if i'm stood in traffic and it gets warm (well ...hot!!) and as soon as i need to stop so does the engine!!!