engine chugging and dying...

I just took my 300zx tt for an hour drive little road trip and when i would be cruising down the road in 4th or 5th gear, it would chug a bit like i was sriving my blazer in really strong headwinds. and then when i get off the highway onto backroads, the car died on me 3 times, and no i wasnt stalling it i was goin between 30-50 mpg when this would happen. could it possibly be the jim wolf ecu and its not tuned correctly? or bad turbo seals?