Don, did you ever get the the bottom of this?
The "Relieve Steering" - if your Cayenne is doing it - try replacing your key battery with a brand new battery. I did - and for several days it didn't happen. I did this due to an error code stored in that module (read it with my Foxwell NT530) of 881202 - "key battery flat"
Now it started happening again, but it makes the "bong" noise and then goes away before I can even start to move my butt into the seat. My WAG is it's supposed to unlock the steering as soon as the car sees the key, or perhaps as soon as you pull on the outside door handle. With a weak key battery it wasn't recognizing the key quickly enough (sometimes indicated by the message on the dash of "Key not recognized"). As long as it doesn't stop me from starting the car I'm ignoring it.
The loss of low-speed steering boost hasn't reappeared since they R&R'd the connector (and cleaned it.) Fixed? Dunno - that happened rather infrequently. I've been meaning to throw the Foxwell on it and see if any codes have been stored recently.
BTW - followup on the shop visit (highly-regarded independent does 95% Porsche)
- Steering boost - cleaned the contacts going to the steering rack and used some dielectric grease on them. Charged 1 hour diagnostics, 1 hour labor and somehow that came to around $300.
- Relieve steering message - diagnostics (which I think consists of reading the notes I brought with me and then browsing the web for an hour hoping someplace else determined what was happening) - 1 hour diagnostics, $165. Conclusion (they admitted it was a guess) was it needed a new locking module which is mounted to the steering column. Module $300 (retail on-line $225, but can't bring parts to this place..) and somehow enough labor to make it a $1,000 repair.
In reading the factory service manual (PDF copy) - replacing the module requires reprogramming all the anti-theft coding throughout the car - about 4 modules in total, and have to have all the keys present. They didn't mention this...
- Loss of brake vacuum - they "looked" at all the fittings and thought they looked OK (guess it's hard to see vacuum leaking since it would be air leaking into the vacuum).. and then they smoke tested the plumbing between the vacuum pump and the booster and saw no smoke get out. They theorize there is a check valve in the plumbing going between the 2 end points (pump-booster) and it's not checking. They want to replace all this plumbing. This somehow also came up to a $1,000 repair. Diagnostics cost - 1 hour again - $165. Mentioned if this wasn't it - then the booster is next at around $900 (on-line price about $400) + installation.
I am still suspicious of a bad connection somewhere since it seems to be losing vacuum more quickly since they looked at it..
So to get the connector cleaned on the steering rack and some "diagnostics", I left about $650 poorer (with 10% PCA discount). Mostly for diagnostics they admit are a guess (no guarantee of success, just keep throwing money and parts at it and hope the issues are resolved.)
I think I'll be talking to Max at Provost Motorsports when he's back from racing and see if he thinks he can fix it. Every time I've been to see him his actual charges are less than his estimate, he charges strictly by the hour and is perfectly happy if I bring my own parts.