From the fuelsaver page:
We pour the majority of our gas out the exhaust pipe (presumably the american use of gas i.e. petrol)

That is arrant nonsense. If only a tiny amount of unburnt fuel were to enter the exhaust, it would very quickly ruin the catalytic converter.

All petrol cars with catalytic converters use some form of fuel injection to accurately meter the fuel, usually using a closed loop feedback system to ensure that the optimum fuel/air mixture is maintained.
see http://en.wikipedia.org/wiki/Lambda_sensorhttp://en.wikipedia.org/wiki/Lambda_sensor

OK, maybe Craigs van doesnt have a cat, but just about all the other petrol cars on the road do.