AAH rough "low" idle (warm engine)
 

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.

Scan for fault codes followed with checking measuring blocks for misfire and lambda values should point you in right direction. Small air/ vacuum leak could be causing this, also IIRC idle stabilisation valve can get clogged up and sticky on AAH, cleaning with carb/intake cleaner or even WD40 usually helps. If you have VCDS you can also activate and exercise it when cleaning to make sure cleaner gets in all parts of it.

Thanks for the reply! I'll rinse the valve to start width.

Sounds like a closed loop condition to me (when engine is warm enough to use all its sensors to run the engine).
Does AAH have a MAF?
If so, unplug it and see if it idles better. If it does replace it.
If it doesn't have a MAF, check lambda as Ainars said.