New information! The bolts for the exhaust manifold for #1 cylinder were loose. I could feel a _little_ exhaust puffing out. I tightened them and it stopped. No change in engine noise though. The missing bolts in the manifold are not supposed to be there. They're for mounting something to the exhaust manifold, and aren't used in this engine configuration. (The mirror image bolts on the other side are used however) I
Discuss this in the forum topic Thinking of buying Cat 963 A high hours.