I don't believe the engine cutting off problem on my 400E was ever completely solved by the Techron additive. Going from eveyone's usefull advice I'm going to start with replacing the Fuel Pressure Regulator (AKA Diaphragm Pressure Regulator)
http://mercedes.thebenzbin.com/?year=1992&make=MB&imageField22222.x=33&imageField22222.y=8
Then if that doesn't do it I'll consider the more costly Electronic Accelerator Pedal actuator control unit. Looks like an expensive part? Anyone ever crack one open? Just curious what might be failing, microprocessor, EPROM loosing its programming?
Here is a pic of things I might try replacing: