Just out of curiosity have you tried checking the fuel pressure when the problem occurs?

Intermittent cutting out can only be a matter of a couple of things, go back to basics. An engine requires air, fuel and ignition to create power.

You have all but eliminated ignition, ignition will missfire or die completely... of which you do not have!
Air problems will be caused by busted pistons or burnt valves, not yet... or AFM problems which may be likely,currently testing... or leaks in the intake which would be constant...so it's not that!
Fuel problems have not even been checked or acknowledged as of yet, perhaps worth a shot.
All workshops carry fuel pressure gauges for diagnosis and testing, maybe someone on the forum can lend you theirs even!
All the best.