had the exact same problem!
check plugs, coils etc. if problem still persists, see your local dyno tuner. That was my scenario....did some runs, ran a fuel flow test etc. I had wrong sparks in, timing was off and discovered the pump was lazy. Replaced sparks and under tuned the car to be safe until I go back and install a walbro. currently organising an arc sidemount to replace the standard one before I go back for the walbro pump and tune.
on another topic, I first witnessed the change in skylines with different climates...goes so much harder in the cold turbos and husky's have much in common.