I've driven nearly 160k miles on this wonderful car. Lately I've noticed that the cruise control, when activated, allows the cars speed to drift up/down a few miles per hour. I'm thinking it may be a vacuum leak as I also got a code yesterday (0172) after the 'check engine' light came on. The car runs fine, and I've begun changing some of the smaller vacuum connectors, the 90's pieces that flake apart when touched. Should I look elsewhere also for this possible leak? I've been to my dealer and they cannot even show me an up to date fische that contains the same vacuum layout of my vehicle. (Has Volvo always been this bad?)
Your help and input is greatly appreciated, as I would like to drive this car at least another 150k miles if not more.

Either the vacuum hoses for the CC are falling apart and leaking, or the vacuum pump under the battery tray is getting weak. I suspect the latter.
As I was recently told by experts on this board, the CC vacuum is totally separate from the engine vacuum. Keep swapping out those engine vacuum lines, and test any check valves you come across to make sure they still work.

Klaus
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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)