This shows the RDK sensors inside a CUP1 rim. One on each side 180 degrees opposite of each other. Each turn provides two signals to the computer.


Der Befestigungsschlüssel 9274, hat die Teilenr: 00072192740, EUR 61,75,
der Zapfensteckschlüssel 9273, hat die Teilenr: 00072192730, EUR 105,28.

Das Anzugsmoment der Befestigungsmutter beträgt laut Porsche-Handbuch 20 Nm

There are two different sensor versions, 2.5 and 3 bar. Both have same shape so they are interchangeable. Stock S4 wheels use 2.5 at front and 3 bar at rear. If one 3 bar sensor was added to front wheel it will give error until pressure is at least 3 bar. Due to how sensors work I think having different pressure sensors in one wheel will work as long as pressure is set above larger sensor value.

There is also procedure for setting up the system which might be helpful to do. '90 MY yearly changes document has several pages which explain how RDK works.