Hello my friend from Svenska!
I'm still trying to solve the pre ignition problem and will try all and any modifications I'll have to make to achive that. First this morning I cut another vent on the cowl on the left side and enlarged the one on the bottom. I also found a restriction on the fuel filter ID diameter was just 3/32" which I enlarged to 1/8", which I think, will cause it to run lean,(the smoketrail has me puzzled) If too small a delivery fuel system : i.e. Fuel lines, filters etc. are too small for the engines demand, it may run, but run lean. But I'm no expert on that and need to investigate this even more.
Am I assuming correctly by saying that you run FAI Fuel without Nitro?, that would be my next step to switch to 5% fuel with about 20% oil just to see the difference.
Thanks again for your input on that subject.