1. Did you checked the mixture as well while driving? If not yet done, this is the time to do so. This is important for the further steps of troubleshoot.
2. How did you checked for vacuum leaks? Honestly - and don't get me wrong - I read this so many times that no vacuum leaks have been found... but too often it turned out instead that there were indeed some not being found before. The one and only way to successfully perform such a test is with a smoke generator! They have small air pump to pressurize the smoke and the system to be tested. Small/tiny vacuum leaks cannot getting identified by cigarette smoke or start spray or sth else! And vacuum leaks are the final boss for a CIS.
When I read that the issue occurs when engine is warmed up leads me direct to one or more a vacuum issues. Also that the engine then starts running lean is an indication for this because the mixture has been obviuosly adjusted with the engine not fully warmed up.
Many people "solve" this problem by simply enriching the mixture because the engine ran too lean because of the additional "unmeasured" air. This works unfortunately for particular operating conditions until the owner claims for some issues like poor running, bad mileage, smell of fuel , hard start conditions etc.
Your measures showed that the CP and idle mixture and the whole lambda control system is ok, which is good. But still I suppose the mixture isn't correct anymore when engine is warm due to other issues caused by other CIS parts than WUR. On a CIS this can easily done by playing around with the CO screw and the sensor plate height and afterwards adjusting the idle screw.
The sensor plate height has a huge impact on the mixture over the whole rpm band. Finally a high idle rpm will be cured by closing the idle screw almost completely.
In these cases I always recommend to make a reset for the CIS and to perform the basic adjustment for it as described in the Porsche and Bosch worskhop manuals. If done, the engine must be able to start successfully with absence of any other issues. I already posted the excerpts of the manuals these days here:
https://forums.pelicanparts.com/porsche-911-technical-forum/1151215-surging-fuel-mixing-drifting-rich.html#post12141568
If the engine then won't start with this basic setup, this proves that there are one or more issues you have to identify then without touching the basic adjustment again.
The only case to touch the basic adjustment again is to make the CO fine adjustment when engine runs again after solving the issues with a certified gas tester which is mandatory after solving such problems.
I know this is an awkward and "upside down" approach to narrow the issues but from my point of view this is the only way to succeed and to identify it's issues. Otherwise you won't succeed in solving the problems of the CIS.
Thomas