BMW 318is Problems

THE warranty ran out a long time ago and there's no evidence that the cause of your problem is the one that led to the 3-Series recall.

I DON'T know of a kit for the E36 BMW. It's one of those cars for which there is little demand for a kit and no one has bothered to develop one. There are universal kits available that could be adapted to your car, but I wouldn't recommend converting it. The 318i in my experience is quite economical, so there's not great savings to be made, but more importantly it's a breathless little beast as it is, and converting it to LPG would rob it of some of what little performance it has.