I believe you wrote 4AO instead of 4A0. Makes a big difference :nod:

brother had a 1997 a4 with same problem i ordered a repair kit on e-bay and took me 30 mins stripping it and replacing the parts, not compicated to do and done the job and a lot cheaper

In very many cases it's not the pump at all. The actuators are in the doors and the vacuum hoses thus run through the boots in the door jamb. Since they're flexed a lot, they tend to crack.

So the first thing to do is disconnect the hose from the pump and check the vacuum integrity with a MityVac or similar.

Yes, I think so.

I recommend it for ur-quattro owners especially because the stock system doesn't lock the car from the passenger door, only from the driver's door.