If you have a fault code its there for a reason. Unless someone has inadvertently unplugged the AFM while the ignition was turned on.
It may be the ignitor more so then the coil and leads.
You really need to check fuel pressure as stated above, if you can have a gauge on when it cuts out, might eliminate the fuel system.
It may also be the crank sensor.
Does it have to be warmed up before it starts playing up?

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F.B. Racing
01 WRX (STI badged)
2010 XR5 Focus
06 Impreza Hatch 2.0i