It seems to me that one unit isn't always working. When it happens spray the exhaust with a plant sprayer and spray the exhhaust bents to see which one it is; there will be no steaming(better equiped people could use a heat gun).
As all the units get their fuel injected at the same time I would not expect a problem with the fuel system as it seems the other units are working OK??

if you would see what happened to my spark plug caps after some asshole put them on sparks without those aluminum little caps, you would probably suspect this at the VERY beginning - i have to start with this one i guess. i'll try to find some car wires first and collect the rest (meaning spark plug caps - total resistance 5kOhm;))

about one unit not working properly - once one spark plug cap fell off and i know how it feels and sounds when one unit does not work for most of the time - it's not so bad with mine, the motorcycle rides, it has power etc, but just sometimes you can feel that weird pulling and then i makes more noise while going up the rpm than pulling power;)

i'll start with the wires and caps, then move to other things.

cheers

paj i have to say that of one plug top falls off ....both plugs driven by the one coil are affected........... but if you have only 1 lead with high restistance /breakdown you might well just notice a lack of power .....
just a thought

You can just use your fingers and I am not kidding.
Just quickly wipe your finger across the exhaust pipe and if you do it quickly enough it won't burn and you will find that the slippery ones are the hot ones and the ones that have a bit of drag are cold.
Give it a try it does work I have been doing it ever since I was shown by a mechanic about 45 years ago.

ok guys, changed the HT cables and the problem is gone!!

thanks for all your help on the matter, seems like you helped me a lot here especially when saying about those little screw-on caps (gracias Charlie99!) on the spark plugs which led me to burned spark plug caps;)

thank you!