Get a can of cold spray. Elecronic components store a good source. Just before it quits timewise. Spray the suspect component. Or just give it random shots, To keep the temperature low. Keeps running you have it. You can usually figure out a way to test any component. Car quits at ldle after a period could help a lot. In spraying components.

Early heavy v8 Mercedes had a strong igniton system I thought. I remember some issues with their coils. That one may be newer that the ones I am thinking about. If the car will quit at idle. Keep cooling the coli.

By now someone has had to establish it is an ignition or fuel issue, Sounds like it has been decided it is ignition. A year by a guy that knows what he is doing? Have to wonder a little.