Chip, from Blue Chip has one on his truck. I spoke with him at some length about the system. Chip put his on... in addition to the stock system so that he could just flip a switch and be running either stock fuel system or Fuel Preporator. He then drove his '99 ISB to Vegas from New Hampshire testing and comparing fuel systems. He said he realized just under 10% improved fuel economy and that the truck does run better. He wants to do more long-term comparisons to get a more concrete estimate of the benefits. He was fun to talk to, very helpful. I've been looking at this thing for some time now and trying to talk to as many as possible about what it does for their trucks. The only down-side most mention, as did HVAC, is the fact that the thing is so honkin' big! But I've looked closely at Brad's system on his truck and it does'nt look too overwhelming... . I think it's a good system. If you read on Diesel Injection of Pittsburgh's website, Bruce Mallinson (sp?) highly touts the set-up... and I think he pretty much knows his stuff when it comes to diesel performance.