[ICCARS]

it sounds to me like you are running extremely rich on start up, so what I would do if it was me is to pull a plug or two and see what your engine is doing i.e. black plugs - rich as hell // clean or slightly greyish plugs OK. Then while you have the plugs out test for a good spark - that will eliminate the MSD.
It almost sounds like you have a change in state in the M48 - I have seen this happen with my M800 as a short or something like that can cause the program to corrupt - it has happened to me and I had to re-load the program and it was all good again.. Computers.
I'm not suggesting you do this at this stage, but keep that in the back of your mind if all else fails, but just keep eliminating every possibility one by one, not 2-3 things at once otherwise you may never find the culprit.

Cheers
Wil