I have and use wood gas. My cousin got a wood gas powered car as a gift a couple of months ago. It is a Volvo 245 station wagon with a 2.1 liter engine year model 1974, modified to use wood gas some time in the early 90's. The former owner said that the car has been driven about 30,000 km with wood gas equipment. However, the car had not been in use for a couple of years and we worked for several weekends to get it back in shape. We have now driven about 300 km with wood gas and learned to use it properly. I personally am quite impressed with the performance: top speed 100+ km/h. I expected much less. We have used pieces of birch wood as the fuel. It MUST be dry or it won't work.
With the car we got quite good documentation of the wood gas system with drawings. The material is currently only in Finnish, but I will translate it into English and put it on my home page as soon as I have time to create it. The information is taken from the research report made by the Finnish research center for agricultural equipment (VAKOLA) in the early 80's. I guess the project was ignited by the oil crisis in early 70's. A friend of mine was working in the same research center at that time for another project and he told me that they had original drawings of the wood gas generator with stamp of the Finnish defense forces. They built a wood gas generator and installed it on a tractor.
Almost all non-military trucks and buses in Finland were operating with wood gas during the second World War and even up to the early 50's. All gasoline available went to military use. I have heard that the Finnish army used a couple of wood gas powered trucks even in 1964. In a local magazine there was recently an article on wood gas equipped cars. The article is in the Finnish language but there are some nice photos. The story says that there are about 40 wood gas equipped vehicles in Finland today. The story is mostly about two persons who have built wood gas generators.
I have planned to build a new wood gas generator on a trailer. This concept has many advantages at least from my point of view. My knowledge on wood gas systems has recently increased drastically. For example now I know that wood gas contains almost as much hydrogen as CO. It is formed when the water vapor extracted from the wood is sucked through the carbon layer and the reaction H2O + C => H2 + CO happens. So I can say that wood gas is definitely a working way to produce hydrogen (and CO) and that one can use it as a fuel to run an engine to create power. So, build one!