Here's the filter I used in my 2001 3.0i:
https://www.amazon.com/MAHLE-Origina.../dp/B0080E4PQS
Mahle KL 96
In the 4th photo on that page you can see the regulator, and the spring clip that holds it in place. I'm pretty sure I remember removing the clip and the regulator just to look at things when I replaced mine a few years ago.
But I can also believe that the individual filters and regulators might come matching only eachother. So if you have a Mann filter+regulator, maybe a Mahle regulator would not fit the Mann filter.