There is some Auto diagnostic information on this page http://www.skylinesaustralia.com/forums/St...ar-t203136.html , its for the R34, but the 4AT diagnostic may work.
Also, run the ECU diagnostic, if you havnt already.
But my first guess would be coil packs, even though they check alright, they are famous for leaking spark to earth around the age of yours.
Where are you located ? maybe someone can recommend a skyline expert in the area, or someone can lend you a set of coil packs. If they are at fault, best option is to get Splitfires, which is what most RB's need to do eventually.
Bad Air flow meter connection? doubtful.