There's a product called liquid moly on this thread that a couple of people have tried to clean the egr. Might be worth considering:
https://forums.ross-tech.com/index.php?threads/27259/
Dunno.if.this link might help either:
https://www.vwaudiforum.co.uk/forum/showthread.php/193422-2-0-TDi-Ultra-CNHA-EGR-and-cooler-removal-and-cleaning/page3
Id say look at maf sensors, crank sensors, cam sensors etc. However you'd expect fault codes if these were failing.
Could it be engine or gearbox mounts?
Don't tell them you've done a obd scan as they might try and wriggle out of it by them claiming you've erased codes which you haven't. Also if you've bought it on finance then you can tell.tge finance company it's not fit for purpose stating your case. Aldo as it's under Audi warranty they should be acting on this. I'm assuming it's full Audi service history.
You've done a good amount of diagnostic work. I'd still advise a diagnostic check to see if there's any fault codes.
I'd still advise getting the battery tested to see if it's failed too.
Glad it's working. I'm going to pin this post and change the title slightly to make it easier for others to find. I do believe it's still naughty Audi wanting to charge a subscription for features in my opinion.
Sorry to hear that. The water ingress issues in Audi's from.this era was ridiculous. Once my A6 has a full restoration (in time) the CCM and all electric modules etc on the floor will be moved.
Welcome to the forum you'll find the members on here are a friendly and helpful bunch 🙂 looks a lovely A4 👍 insurance companies do like to drag their heels.
If it's hydraulic operated I wonder if the roof coming down on its own under the weight and pressure has damaged the pump. Is there any noise from the pump? Also id recommend a diagnostic check to see if there's any fault codes.