Hey Mate, I saw your post and I'm having the same problem of your car.
It's a Ford Falcon BA XR6 Turbo - 2004
The car run really smooth, but sometimes it's cut out and doesn't crank anymore. I have replaced a lot of parts and nothing... The last one, I replaced the starter motor, replace the battery ground, throttle body.
I hope you already find the problem of yours, could you give me a light? I already went in 4 mechanic shops different but no one found the problem.
NOTE: I noticed that when it cuts, the fuel pump and starter motor don't work. After a few minutes it starts working intermittently.
I'm very bad because I both this car 4 months ago and since I bough it I didn't use one day without this problem.
Thanks a lot for your help.