Im having almost exactly the same issue. My problems started after the car sat idle for a few months while I was overseas.
At first it seemed like it would only occur when running up a hill, but not every hill, just say one in every 50 for example, but it seems like the problem has evolved as it now occurs on any or no incline. This also happens randomly at any speed, and/or anywhere in the rev range.
In the same way as cactus stated, when the car runs, it drives like a dream. But the cutting of power is completely random. Its pretty safe to say that the car will work fine for at least 10 minutes at the start of the day, but anywhere from 10-30mins of driving, at some stage the power will cut. It may just be for a second or two and then continue on, or like what happened on the freeway the other day. Driving at 100, power cut, never came back, rolled to the emergency lane.
Sometimes you can restart the car immediately and continue on your merry way, but what is happening more often now is you have to sit for a few minutes before it will restart. I have a power fc with hand controller, and there is nothing crazing going on when I watch the voltage readings from the AFM. There also no coughing or hesitation of the engine, so its not like the fuel pressure is simply dropping, its almost like the ignition gets cut. My water temp is sitting at around 70º normally, but its not like its spiking at the points of stalling.
The car has had its coilpacks replaced, new spark plugs, cleaned all ignition loom connections, AFM sensor and connector cleaned, fuel filter replaced and a new air filter for good measure. All of which has made zero difference. The car is running the standard fuel pump, but I do have a spare 040 kicking around that I will swap when I get the chance, but like I said it before the power loss is to instantaneous, seeming more like its on the electrical side of things.
I'm really hoping someone can shed some light on this as its becoming quite an inconvenience.
Cheers