I just dealt with this at two CT dealerships. First was insistent on full diagnostic at ~$650 and would not accept that there is significant community evidence and a TSB to simply check the software version and update.

Initially, I had similar stance from the second dealer but they compromised with me to charge the time to perform the update after being very persistent about the community experience around this issue, the existence of the TSB, and harping on the "previous bad experience" I had at the first (competing) dealership. Of course, they were "unable to confirm issue" despite my videos, but my software was in fact out of date and the update made a significant and positive change. I paid for 1 hour of work ~$305 total.

I have some more details in this thread https://rennlist.com/forums/cayenne-...o-issue-3.html

 

for reference in case it helps anyone's cause:

 

Note: Loss of boost is typically when vehicle is very warm, like 1 hour+ of highway driving. There is almost no way a tech will be able to verify the issue on a test drive.

 

car was warm from having just driven it there and arranging "while you wait" service appointment

i also disagree with you, this problem manifested at any engine temp.

 

For me it first started happening toward the end of a 7-8 hour long drive, but after that first time, it started happening on shorter and shorter drives, as soon as the was warm it started having the issue and I was able to make plenty of videos showing the speedo with the boost gauge showing the initial rise and drop off boost pressure.

 

Recent 2017 Cayenne S purchase from original Owner, 85k miles. Between my wife and I this is our 7th Cayenne and it was real easy to tell the turbo was not doing its job. Same symptoms as all the above in this thread. Power drop after shifting into the next gear, losing mph in cruise going up a hil, etc. So I have a thought, will a Softronic tune fix the problem or is it better to take it to a dealer for the update?

 

Not sure, but I thought the issue was the knock sensor is too sensitive when the engine is hot. Not sure if a tune fixes that.