Hi! My 2001 Nissan Xterra, RWD, with 4WD option, drives fine in town but after a while at highway speed will lose pressure on the gas pedal and will slow down rapidly and then eventually die. After a few minutes it will restart and will get back up to highway speed and will sometimes drive without dying the rest of the trip or it will happen again. Any idea what could be causing this? Thanks so much!