If your BMW 2002 has developed an exhaust leak at the manifold or vibrates at 2800-3000 rpm, then some of your exhaust stud nuts may have worked loose, or even fallen off any of the eight studs which secure the manifold to the block.
Tighten with a 12-mm wrench and the noises disappear. You may wish to remove the manifold cover for better access to the lower four studs. To avoid this problem and the related problem of broken studs, get in the habit of tightening your exhaust stud nuts every 8,000-10,000 miles as the factory service schedule indicates.
Author: Craig T. Reisser