I'm working on my wife's A6 (AVK) with 98K miles, and while I have the heads off I thought I would replace the valve stem oil seals. All was going well until I got to removing the exhaust valve cam followers. All 12 followers have various degrees of pitting on the wear surface and definitely have to be replaced. The inlet followers are OK, but I will replace them as a precaution. Fortunately the camshafts are in good shape with no measurable lobe wear.

Is the exhaust cam follower wear a known issue with these engines ?or do I need to look at the lubrication system. The engine has always had Mobil 0W40.

Any one know if there substitute for the Audi sealant AMV-18800102 to seal the cam carrier frame to the head ? The Audi stuff is $72 for a 100ml tube from ECS, $98 from the dealer.