Not being funny mate but it sounds like that machanic doesn't know what hes on about. Theres 3 things on a plate on the bulkhead:

1. MAP Sensor
2. EDIS4 module
3. CO Potentiometer.

I'm guessing he's talking about the EDIS4, which is what has the basic spark settings in, which it calculates from the CPS. The ECU then takes information from all the other engine sensors and modifies the signal and sends a SAW (Spark Advance Word) to the EDIS4, but if something fails the car will still run from the EDIS4 alone but with compromised performance and economy.

If the car starts, and runs as normal from a tow start, its extremely unlikely to be anything like that. If you understand what im getting at?