Maybe crankcase breather?
If a piston is cracked then you will hear it blowing and misfiring + it usually smokes blue on part load.Hi Chris, thanks again for weighing in.
I will recheck the N75, and then the pipes on the weekend.
The smoke from the filler cap is not oil smell but stringly of diesel.
As i undrestand, this diesel can come from the injector before the cylinder, or from within the cylinder (hole or crack in piston).
I will get the injectors pulled and checked first.
If i cant solve this quickly (I need this car as a daily drive) i may have to offload it....