I've seen some discussion on this site regarding the merit vs cost of water injection for gasoline engines, so I thought that it might be a good idea to post my experience on the topic. I once inquired with Aquamist in the UK about water injection for my truck. The engineer there told me that unless I was running a super/turbocharger, or high compression, that the water injection system would yield only small improvements in performance. He actually recommended that I use a very simple "wet sponge" set-up. This set-up uses a common household sponge glued into the airbox. The sponge will likely have to be cut/shaped in a way so as not to restrict air flow. Small drain holes should also be used to prevent excess water in the air box which could cause hydro-locking. The sponge is then kept wet by using a small pump connected to a water reservoir (a windshield water pump and reservoir is ideal). The idea is that the wet sponge humidifies the air box and the intake air. The system works on the same principle as a home humidifier. The pump is controlled by a dash mounted switch. The down-side to the set-up is that it requires some trial and error to find out how often you need to trigger the pump to keep the sponge wet. The up-side to the set-up is that it is very cheap and simple. I am going to try this set-up on my next RV, and I will let you all know how it works out.