just had to do all my plugs, they had deteriated but nothing had shown up. then suddenly iwas unable to run on lpg. changed plugs and its perfect now.
you can get the cable and software for most lpg controllers from ebay. if its a leonardo controller, like mine, i had a fault on one pcb inside the controller that wouldnt allow the stepper valve to open.
it sounds like a service is needed. if your happy to do it yourself then its pretty straight forward, a lead and software is essential tho to set up the lpg system. it is practically a carberetter(not very much different) and with the software you can tune it up in pretty much the same way you would a carb. you can get it something like by ear but it takes a bit of practice to do that so if your new to lpg then i would get the software!!
let us know what system it is(controller/computer) not the vapouriser. and i'll track the software down.