They should know how to check fuel pressure and flow. If either of doesn’t meet specs then investigate further. Or you could just guess it’s the fuel pump.
Guessing which part has failed can be an expensive way to fix a car. But eventually you will guess correctly!

Update: After a lot of testing (electronics, fuel system and pressure, etc.) the cylinder head temperature sensor was replaced. Car was ran for extended periods without issue. MAYBE it's fixed this time???

Thanks again for all the input!