The master cylinder is NOT part of the powerkit, this is why the initial brake feel is a bit softer than with the OEM brake. Sorry, it seems I overlooked your post.
My Cayenne Turbo has now almost 20000 km and has been driven hard most of the time, including some high speed travelling at over 270 kph (168 mph) on the speedo from time to time. My only technical problem was a that damned micro-switch of the rear hatch window which has to be exchanged twice. I de-activated the electric mechanism recently because I found the rear hatch window open again and Porsche doesn't seem to have a "final" solution yet. The cooling liquid loss I reported after my Italy vacation was a one-time incident, apparently there wasn't enough cooling liquid in the system from the factory and I had to add over 1.5 litres to cope with it. Since then, no loss anymore. So far, the Cayenne Turbo has been proved to be my most reliable Porsche and with the exception of my wife's SLK 32 AMG, the most reliable car I ever owned (and I owned a lot over the past 21 years).
I know that some people had issues with their Cayenne but I really think these are exceptions. Same with my 997 Carrera S: some people reported problems with the eletrical system and some (still unconfirmed?) RMS issues. The only problems I had were with the gearbox and the clutch, probably due to the fact that the car was one out of a bunch of "production start" cars, built in march 2004. The gearbox manufacturer apparently forgot to add a certain initial additive to the gearbox which was needed for smooth shifting. The gearbox didn't brake down and the clutch didn't let me down suddenly, I just had problems with enganging the 1st gear and the clutch made a horrible howling noise at low temperatures. Both have been exchanged on warranty without any problems and now everything seems to work fine. No engine problems, no electrical problems, nothing. And I really don't treat my cars with a lot of caution.
So in my personal opinion, Porsche doesn't have ANY quality issues but SERVICE issues. It can't be acceptable that a customer has to talk several times to a dealer to get things done or that a customer is kept days or even weeks in the dark if Porsche pays for a certain repair under warranty or not.
The attitude of SOME dealers and SOME Porsche employees (most of them are very nice, I had to deal with them personally and they really try to help) has to change because they're not selling a Volkswagen but a top of the line sportscar or premium SUV.
And finally, there is another thing I don't understand and maybe you guys can help me out with understanding it: over here in Germany, a Porsche mechanic earns the same money like a VW or Skoda mechanic. For me, this is not quite understandable. I would pay them more, even much more but send them to training classes and even put them through some sort of exams. How do I expect from a mechanic to do a first class job if he doesn't get first class pay? Do I sound irrational? Maybe. But I really sometimes have a bad feeling when I imagine that somebody works on my brakes and steering but isn't paid like he should be paid. Maybe it is just me but I really think that Porsche should train dealer mechanics much better. Some of them are great, my chief mechanic doesn't talk much but he is very reliable and knowledgable. Yesterday, his shift ended at 5 PM but he stayed until 6:30 PM to make sure that my Cayenne is safe and everything is within specs. He testdrove it himself and checked everything. And finally, he even wanted to wash my car but I told him to forget about it and go home.
Over here in Germany, this is NOT something common. Workers over here are very "anal" about working hours and ending of working shifts (thanks to their beloved unions...
).
Overall, I'm pleased with Porsche quality, I just wish the service and the attitude would be improved too to cope with the "social" status of their cars in the car world.