AAH rough "low" idle (warm engine)

[OlemTheGolem]

Hi! Last year my engine started getting very rough on idle after a drive. Cold it idles just perfect @ 900-1000rpm, however when it gets warm it will be rough to the point I think it might stop but it doesn't. Since August last year I replaced the spark plugs and the rough idle went away. However now it's back and worse than ever. The car has done about 5k miles or less since plugs where replaced. In two weeks I'm heading off on a 1000km+ roadtrip in this car with 345000km on the clock. Anyone who had similar problems and have any suggestions?
At speed and above idle it's smooth as a baby's bottom, surprising to me having owned other cars at this age and mileage not doing that well.

Over the last week I did a service on it replacing engine oil & filter, tranny oil & filter, fuel filter, coolant flushed and replaced with g12+ and cleaned and oiled my h&k panel filter. None of this did seemed to do it any favors.