Towcat is right about the DS4. There is supposedly a correction for that problem something about a heat sink? The problems I see are 1) I'm very skeptical that you'd see any mileage increase with it let alone 5 mpg becuase I usually hear that the 6.2s got better mileage than the 6.5s. I may be wrong but it seems to be the case. 2) The GM setup was a mirror image of the Ford DB2 pump as some here put it, they turn the opposite direction. Ford never used a DS pump, they went right from the mech injection to the PSD, so finding one that rotated the right way would be difficult or impossible 3) If you had one fail, a factory DS4 rebuild runs closer to 1000 than 500 dollars. I know a guy that tried running his 6.5TD suburban on WVO and wound up replacing 2 of these pumps at well over 2000 buck total...ouch!! Good thing he's a lawyer with plenty of coin.