Surely there's a page in the technician manual that alludes to the running measurements on the sensors? Voltages, resiistances, etc?
It sounds like it's intermittent, so it could well be a contact inside anything that affects the car's base map to allow it to drive - MAF, crank, coolant sensor etc.
Is there any way of getting a mate to watch the fault codes on the reader while you drive and see what it picks up when the car does eventually fail?