Thought of something else today, it should have hit me right away but somehow it just didn't register... Are you certain that you have the timing correct? I assume you had the cam gear removed when you took off the head, because you kind of have to. If the chain slipped a tooth on the sprocket it would do almost exactly what you have described in the first post.

__________________
Alex
MB Star certified, now independent.
Owner/Operator FDMotorsport Mpls. MN
Mercedes and GM certified transmission rebuilder
We all need a little help sometimes...

1998 E320 4MATIC-- stolen by my sister
1989 300TE-- sold
1999 C230 Kompressor