Audi Turbochargers: Differences Explained

Hello.
I had to replace the turbocharger on my 2.5 TDI.
The new charger has the same part number, but a different letter at the end.
Now, sometimes the engine revs up very quickly, and other times it revs up to 4,000 RPM and then seems to hit a limiter.

Question: Could the difference between the chargers possibly be due to the vacuum sensor?
Can I take the vacuum sensor from the old loader?

Thank you in advance.

Jörg.

@udi wrote:

The new loader has the same part number, but a different trailing letter.

Is the other ending letter just an extra "X" (for exchange part) at the end, or is it actually a different part number? Please provide both here.

Generally, with VW/Audi, the complete part number, including the trailing letters, is crucial. It's possible that the letter at the end only indicates the revision (e.g., a larger letter might signify a newer version), but there are also many parts that are completely different (e.g., from a different supplier, or for a completely different application).

In the first case, it will probably work with a different letter as well, but in the latter case, it is sometimes completely incompatible.

Therefore, here are some more details:
a) Which part numbers?
b) New part or replacement part?
c) Source?

Greetings.
Guste.

And don't replace the vacuum tubes... that won't make it any better. First, try to narrow down the source of the problem.