soundquest

2012 A6 3.0 TFSI. Performing water pump and Tstat replacement and am planning to service/replace other items while I've got more open access with the supercharger removed (oil seaparator, breather hoses at the rear if they break on removal, spark plugs and coils, longitudinal coolant pipe, oil filter housing). And if i can procure a walnut blaster and attachments for this platform... I will do that as well. What else shall i opportinistically replace/service/inspect while i am in there? Thanks in advance.

Valpo A7

Water pump and T-stat - good idea
Hoses/pipes - replace if needed
Oil filter housing - ONLY if needed. No reason to replace if not leaking or broken. If leaking might just need seals.
Spark plugs - if they are due then go for it, don't need the charger off to perform service
Coils - ONLY if they are bad (my coils were still original at 234,000 miles when I sold the car)
Coolant temp sensor - not a bad idea since the coolant will be drained
Fuel pressure sensor - not a bad idea since the charger will be off.
Both belts if they are due with service mileage timeframe
Consider a new PCV if you are consuming oil

Carbon Cleaning - good idea if needed. I put long highway miles and used 89 octane fuel (not really sure if it was top tier but I shopped at decent gas stations) Previous owner had an Audi CC done around 105,000 miles and I never needed it by the time I sold the car at 234,000 miles. Had 1 time on a trip around 210,000 miles that it was running a bit rough and I ran 2 tanks of quality fuel injector cleaner through the engine at highway speeds and never had issues after that. You get less deposit problems with drives over 30 minutes.

soundquest

Good suggestions (and sorry for the delayed reply). Thank you. Luckily, those items (belts, etc) were addressed by the PO just before I purchased it. However... I do want to make sure I address all the cooling hoses/pipes while I am in doing this job. I have added the crossover pipe to the list but am wondering what other cooling pipes/hoses should be replaced. Also -- how often do the supercharger cores go bad on these and start leaking? What kinds of symptoms/signs do they present with when they start to leak? Open to suggestions and ideas on the above areas as well as any breather or vacuum hoses that could also be replaced opportunistically. Thanks again in advance.