A4 gremlins?

I've been having a problem with my '97 2.6 V6 A4 since about the start of the year. It dies at the most inconvenient times, freeway, in a roundabout. Normally restarts and may not reoccur for weeks! Mechanic looked at it on 3 occasions, no fault reported by computer..... Finally last Friday night it died - all dashboard lights flashing, including low fuel even, locked in Park, even central locking locked! Managed to get it off the road, had it towed to my service man. It's got to be electronics right? Is there one central chip to replace or more? I know he tried hot/cold on the EMC (?) to try and force it to go.... I'm in Perth Western Australia