My car has this problem as well, Here are my ideas on the subject..
I have noticed that my stalls only occur when I have my headlights and other electrical devices on or when I have little petrol in the tank. It rarely happens during the day.
I then noticed that the battery in my car is rated at 280 CCA, which is miles to small for a Skyline.
What I think happens is when you have your lights on and stereo going and come off the gas at 3000rpm. As the Revs drops so does the current coming out of the alternator, when you go below 850-1000 rpm your alternator can't supply enough current for the whole car. Then fuel pump doesn't get enought current and then you stall.
I have also noticed that the car doesn't stall when I have a full tank of petrol. This is because of the fuel level in the tank, the more fuel the more downward pressure (due to the effect of gravity on the liquid) on the pump (or for the engineers in the audience NPSH). As the level drops this pressure reduces and makes it hard for the pump to work effectively. This combined with low current from the battery and a clogged fuel filter will make a car stall.
I'm going to replace the battery with a 520 CCA model some time this week and replace the fuel filter thie weekend. Should sort it out. (Sorry about the long post peoples)