I found a site after doing a bunch of research on hydrogen, hydroxy, and O2 sensor modifying.
They sell some incredible products, including a MAP or MAF sensor attenuator to fine tune your engine for optimal fuel economy, different stages of hydroxy producers as a kit, and isolators to remove your O2 sensor from the exhaust stream to counter negative results from the use of added hydrogen/oxygen to your engine. Some kits even have measuring devices to measure actual hydroxy production in LPM.
Read some of the testimonials and you will see claims like one fellow, driving an escalade, who now gets 53 mpg. running their 'Optimizer' (air/fuel mixture control).
These systems apparently will install on any fuel injection system, and there are even carb systems available. They supposedly are launching in April 2008, a 'Protium Injector' that generates 100% of your fuel as hydrogen!? No onboard hydrogen storage, either.
Does anyone here have one or more of their products? I am seriously considering one of the deluxe kits with all the devices. I was gonna make my own bubbler, but after seeing the quality of their stuff I think I will be better off buying theirs! Oh, and the best part? I see they offer 100% satisfaction, guaranteed 20% increase in economy (on at least one of their devices), or all your money back. The prices are too good to be true, and the devices should pay for themselves quickly. Tell me what you guys think. If I save up and buy a system I will start with my Tempo and post my results when I have them.

http://www.protiumfuelsystems.com/news.html