V70 MJ 1999 B5254T false ignitions (only!) in idle mode with warm engine

my (soft)turbo brick has been making funny things for some time. 1. at charging pressure, it is clearly audible from the engine compartment. 2. at operating warm engine there are sporadically/without pattern misignitions on cylinder 3, but ONLY in idle run. not at higher speed, not at partial load, not at full speed. one hears it in idle also from the exhaust and sees it through small speed breaks. new ignition coil for cylinder 3 has unfortunately not fixed. another suction bridge (without the whole (ve It can be that it somehow pulls in the empty run false air, thereby the mixture (why only cylinder 3 ?!) becomes too lean and by the same “leckage” the charging pressure hissing escapes ? the Longtime Fueltrim is about +10%.. is that within the framework or could this be related to it ? I abe soon an appointment in a tuning workshop, which has equipment for the Le ckage search in charge air systems.. I’m curious where it whistles out everywhere.