hey mate
i had a similar problem a few months ago, car would stall when in relatively low revs, and occasioanlly when just coasting, it would struggle to hold revs then just die, regardless of clutch position, and throttle position, after painfully inspecting all the wires from the ecu, and wanting to avoid taking the car to a workshop i replaced things on my own, new plugs on throttle position sensor, new spark plugs (found last tuner used wrong ones ), i did all the cheap stuff first and then moved to more expensive parts, hoping i didnt have to get a new pfc. anyways, long story short it was the air flow meter, so if u have a chance, swap urs for a freinds n c if problem persists. i got mine from crd (Z32 AFM) and those guys are wicked for service n pricing. hope that solves your problem champ, theres nothing like walking through a tunnel with no light at the end haha.
cheers
Slav