A friend of mine has been tinkering with a hydrogen booster that can run on gas or diesel engines. He swears it works( Although I don't think he has it installed yet) & can give you up to a 40% improvement in fuel economy. I am interested but also not convinced it is not just another bunch of snake oil. It gives you the plans to build one & how to install it. I would love to get some opinions from you diesel placers whether this might work. To me it seems to be too good to be true. They make it sound very convincing though. They also are not requiring you to pay any money. The plans are free to download. I see there is already one thread one here about hydrogen boosters/generators. I was going to add this there but I didn't want to hyjack that thread.
http://www.smacksboosters.110mb.com/