955 Cayenne Turbo what to look out for

[Walter Sobchak]

I'm hopefully going to look at a couple of these this weekend to replace a 2.7 diesel RRS, have decided for the amount of mileage I do it's not really worth the extra for the 4.8 so looking at a couple of 4.5s with between 60 and 85k on the clock.
Could anyone tell me the main things to check have either been done or will need doing on them?, from what I've heard the turbos are pretty reliable.