Based on what you've shared so far regarding the failure (just stopped, no unusual noises, etc.) and your attempts to diagnose, my best guess is the crank position sensor (CPS) has gone bad. As a result the engine computer has no idea where TDC is for each cylinder and can't determine when to fire the spark plug.
The only other reasonable possibility is a huge vacuum leak. One of the AOS hoses could have come loose or some other hose of a similarly large size. Check everything that connects to the intake system -- both ends of each hose and the hoses themselves for splits/cracks.
It is unlikely that the coil packs are bad. All 6 don't fail at once.
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-- John
'00 Boxster S
'86 911 Carrera Coupe (Sold)
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