Audi S8 D2 hesitation on the revs

[H24k]

My S8 D2 40v has a slight missfire on idle, basically when I start the car it sounds ok for about 20 seconds then starts to slightly missfire and run rough,

when I rev the engine it holds back for a second then will rev ok to the higher rpms however on idle it allways does this,

I changed the spark plugs as they were all knackered and was sure this was the problem however still the same and I had one coil pack that looked worn out so i changed that but still no difference,

the car drives ok as its moving along seems to have the correct power and engine is very smooth on the go however as soon as i come to a stand still and try to pull off theres a lack of power and the rough idleing like its running on diesel! lol

I cant see any holes or gaps in any of the hoses, and the engine seems fine apart from this!

The car needs a new oil cooler which I was about the have fitted however Im trying to find out if the engines ok and there is no other major faults before i start spending money on it!

[Adrian E]

Another coil pack would be worth a check - if you have vcds you can log which cylinder the misfire is coming from which will narrow it down.