Okai, put in my new LPG converter.
Hooked up all the coolant, got a new brass pipe made up to connect converter to lock off.
Played with the idle/mixture screw till it ran nicely.

Now, I can hear a slighhttt hissing noise and a smell of LPG.
I found out where it is, can feel the gas coming though.
Setup goes, lock off -> brass pipe -> adapter -> converter

Now its leaking through the threads on the adapter where it screws into the converter.

Its a new converter and new adapter, and theres only one size that can fit. So its not like its a wrong size or something.
Can i put thread lock or some sort of sealer on the threads and once its cured it will stop any leaks?

I don't know a hell of alot about car lpg systems but I can tell you that at work we always use thread tape when using lpg gas. The green thread tape is best as its for high pressure systems.

autogasket red sh%$

or pipe sealant

most pipe fittings are brass so try tighten them up more check for leaks with soapy water in a sprayer

Just a tip dont drive it on gas whilst its leaking.... Try some of that tape and to test use a bottle of water and some dishwashing liquid give it a shake and spray around all the gas fittings you played around with. If it bubbles you have a leak. Or do what my uncle did use a lighter... lol... "Dont use a lighter only joking"..

"Just a tip dont drive it on gas whilst its leaking...."
lol of course, i thought that goes without saying, but then again i guess some people need to be told.

I got some thread tape for LPG use, rated at 2.6mPa. (same rating as converter)
Pulled apart the connections and wrapped them up (the non leaking ones too just to make sure)
works like a charm, not a single leak :D

Cool sounds good but test it on a frequent basis initially just in case. As you are probably aware metal expands and contracts when hot.

Regards

mmm good point, suppose the answer is more thread tape. :)

Thanks everyone for their help again.