What do you mean by "good"? Good as in working? If it's not honking
and if you're able to hold boost, it's working.
Or good as in 710N as opposed to a 710A, which is the stock DV on an a4?
On the outside, they look identical. You'd have to take it out and find
the part number that's printed on it (black on black unfortunately).
One says 710N, the other says 710A.
It's actually a real pain in the ass to get to on the A4. Start by
getting under the car, taking the belly pan off, and looking up near the
bumper on the driver's side. If you still have your original BPV in
there, make sure you have spare clamps because the ones that are on
there are one-time use, so after you take them off, you won't be able to
reuse them, at least some of them.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.