Howdy everyone!
Just some quick background as an intro, I purchased a 04 Cayenne TT last weekend with 57K miles down in Ft. Lauderdale for use by my wife as a local daily driver. So, right now I'm in the process of de-bugging the vehicle to make it as reliable as possible. According to the local indy shop I'm using that services Porsche I've got one crushed transmission mount, the motor mounts are tired (but not bad), and they had the feeling something was loose in the suspension but they weren't sure - air struts all raise & lower the vehicle OK. From the initial inspecton it seems to run & drive OK however, no leaks or squeaks. I'm doing tires all around next week on a labor day sale (the last owner mixed two different brands of criminally cheap imported tires, I found major sidewall cracks in one tire after a 5-minute inspection!) and I've been doing some EBAY for nickle-dime replacement pieces.
My local Porsche dealer did NOT win my initial vote of confidence yesterday, I went down & made a small parts order and asked if they could pull a service history on the vehicle for me to see if I had the coolant pipes upgraded, they used the line on me that "our computer system is not hooked to other Porsche dealers and you'll have to visit each individual dealer that serviced the car for a complete history". Yeah, right. And I'm coming back to your service department really, really soon..... hear the cold wind blowing? 
Anyway, to the point of the post. During my initial inspection, I heard and two other competent folks heard some rattling at the front of the engine. It wasn't the constant "tap tap tap" you'd get with the tired piston syndrome on the 4.5's like I've heard on the YouTube videos, but just a mid-frequency rattle of low to intermittent occurrence. Once I thought I had a whiff of coolant but I'm not sure. So, to err on the side of caution I'm probably going to do a water pump and at the same time do the coolant pipe changeout along with whatever T's I can replace with metal subs while the engine's open.
Water pump brands. I know there's multiple manufacturers out there, OEM Porsche, Laso, Hytec Debartolo, Gates, Bosch, ASC Industries, GMB, and the list continues. Anyone know who has the best QA on the pumps to hopefully stave off another failure? Granted the first pump (assuming for discussion it is the original pump) lasted 10 years, but does anyone else stand out as superior?
Also... on the coolant pipe replacement, I was considering strongly using the revised ECS Tuning kit. They seem to supply everything that's needed along with some extra, also ECS has a good reputation from folks I've talked to. So, has anyone used their kit as opposed to the one from the Porsche dealer? The ECS kit is $599 plus shipping. Here's a linky:
http://www.ecstuning.com/Porsche-2004-Cayenne-955-Turbo-Sport_Utility-V8_4.5L/News/Porsche_Cayenne_S_Turbo_Coolant_Pipe_Upgrade_Kits_2003_2004_2005_2006/ES2594479/
Thanks for input before I start shelling out major $$$!
Eric