Well ive got 15000ks on the Navara & it has started to want to rev above 3000rpm so fitted chip today.Its like driving a different car,wants to get off the line,revs out much quicker though all gears,still only taking it to 4000rpm but wants to go to that rpm where before it ran out of puff at 3000.Now I will be keeping an eye on fuel economy & will let you know.Hugh