RB30 Dizzy dust problem

[Booster]

Hey all. I've got a problem that I and many others have never seen before. I have a rb30 on lpg and turbo running an MSD 6BTM ignition module. Now the problem is the distributor cap. After about 130km the engine will start to missfire under light load (when accelerating in traffic) and the distributor cap is full of black powdery dust. Now its not carbon build up as far as I know and if if was then I have a serious problem because it is about a 2-3mm thick coating on everything under the dizzy cap after only 130km. I have put in a new CAS, rotor button and dizzy cap and it is still filling up with this dust. What can this dust be? I've checked all the moving parts from the dust cap up and there doesn't seem to be any rubbing marks of wear on any of the plastic parts. Could there be something in the CAS rubbing on the shaft? I'm stumped and so are all the other people I've spoken to which includes 2 mechanics of 20 years. Is it oil making its way into the dizzy cap and burning to create a black sooty dust? The dust is not magnetic and smells like burnt plastic but I cannot find any material missing from any of the parts. Another theory is that the spark is so big or the gap too large that the spark is burning the distributor cap layer by layer resulting in a perfect looking cap but slightly thinner. The contact points look brand new except for black scoring marks from the dust burning which wipe off with some contact cleaner.

So if anyone has any ideas on what it could be throw them my way.

Cheers