AU2 LPG won't fire.

[FalconXV]

Ok. I bought a cheap AU2 on gas with 140 xxx kms, thinking safe bet, good trouble free investment.
Little did I know, the last owner has neglected the sh** out of it. Front springs have been cut within an inch of their life, rear tyres are retrograte 205/R15!, original motorcraft leads, neglect.
I did about 8,000 kms before a backfiring problem develops, below 2000 rpm. This goes on for at least a month, with some cringe-inducing backfires, which I suspect blew a hole in the flexible rubber inlet pipe.
Against my better judgement, I pressed on until it cut out one day, and wouldn't start.

Got it towed home, fitted 6 new plugs ( NGK non-iridium), new leads. Does not fire on 3 cylinders. Reluctantly cranks over sometimes. Buy a new coil pack, same issue.
Thought it might be leads, as when I tested spark, it was intermittent on 3 of the cylinders. Replaced the leads, won't even kick now. (Top Gun leads).
What do I do now, I can't afford to get it towed to a mechanic, and I am goign to see if theres a repair manual I can borrow at the library, or pdf.
Could it be a sensor issue or am I way out of my depth?