Audi S8 D2 rough idle and missfire

[H24k]

My audi S8 facelift D2 has a rough idle however when the engine is revved past2 or 3000 revs its nice and smooth but on idle its running rough like its misfiring,

I changed one coil pack which looked faulty due to the rubber being all damaged etc but this didnt make no difference, Ive checked all hoses for splits but there are non, Ive taken throttle body off and cleaned it and replaced and also taken off the pcv valve and this was completely gunked up with oil and some other gundge, and also the pipes attached to it were full of oil and stuff and i cleaned these out as best I could, the diaphram in the pcv valve is fine, after doing all this the problem is still there!!!

Basically if I blip the throttle I can hear almost like an air sucking sound and the car wont rev freely, it doesnt rev straight away and just makes a slight sucking sound which seems to be coming from around the back where the throttle body is! Does anyone have any idea of what could be causing this?