Just wondering if you guys had thought about water injection as a cheaper alternative to gas?
The main aim of it is to allow engines to develop more power (spitfires used it) but another plus is that it can make an engine more economical by providing a more efficient combustion, which is why your car seems to go better on a misty day.
Short article here -
http://www.motherearthnews.com/library/1979_September_October/Water_Injection_Wizardry
Many years ago I had a very simple set up on a MGB which consisted of no more than a plastic bottle, a plastic pipe & a nylon injector which went into a vacuum pipe. It just relied on engine vacuum to draw the water through the injector & atomise it. Things seem to be a bit more techinal now with pumps & such, but for a couple of hundred quid it may be a more viable alternative. It is WW11 technology, so is more in keeping with the vehicle. 8)