My stock '97 7.3 w/163K has been running a little rough in lower speeds (20-40MPH and 1000-1500rpms) but no noticeable surging of the vehicle. The engine sounds like there might be some restriction in fuel flow. Once you get up to highway speeds (55-60mph and 1600+rpms) no noticeable fluctuations. With this junk low sulfur fuel we now have, I always use either Ford or Power Service diesel fuel additives upon fill-ups (using white bottle, winter grade w/cetane boost now). Been pretty cold up here lately; -44F last night and was thinking of adding some Iso-heet (red bottle) to the fuel as well to see if that corrects the problem. Anybody ever do that combination or think that may be too much alcohol additive in doing so? Thanks in advance.