[boss11]

I owned a 04 955TT for about a year and had quite a few issues, the coolant pipes were done, however the coolant tee behind the engine went resulting in all coolant being dumped on the road..
Also had to replace a coolant expansion tank few months later as that also developed a leak. Had numerous vacuum leaks as some of those plastic pipes under bonnet get really brittle from the heat that engine produces.
Few months later it wouldn't idle, I looked at ignition coils and 5 of them were cracked, looked at spark plugs and 2 wells were full of oil. Changed all plugs, coils and valve cover gaskets. That did not fix the problem but eliminated any misfires I was reading with Durametric. Upon further investigation I found voltage fluctuation in one of the Air flow meters. Unplugged both MAFs and car ran perfectly. once I installed the new MAF the issue was fixed.

Check engine lights were quite a common occurrence in my case, I recommend Durametric as it saves a lot of trips to the dealer/indy. Based on the codes I would get my cats were on their way out. Also while investigating my no idle issue I came across cam deviation angles which were outside of tolerance indicating chain stretch.

Also had issue with fuel tank purge valve, not an expensive fix but another check light nonetheless.

It also leaked water into the trunk somehow amongst other small issues like headlight connectors going lose and stereo going mute intermittently etc.

I did love the truck and got quite accustomed to constantly working it, however in the end decided to sell it while nothing was "broken" and replaced it with E55 AMG which has been great so far.

So my advice to OP is buy one that has the coolant pipes and Tee done. Take a Durametric tool with you when looking at the truck and check for misfires, cam angle deviation and any stored codes that may not be causing CEL yet. Ask when the coils were changed and budget for them if they haven't recently.

If the heart is set on Cayenne and if the budget allows - go for the turbo model, it is extremely fast and has loads more features than the S.