Brice, The page you referred to http://www.sjmautotechnik.com/TROUBLE_SHOOTING/vac.html has information for the 1986-88 5000TQ and the 1989-90 200TQ with the 10V Turbo engine. The section on valve cover gaskets discusses "vacuum" leaks that can be caused by a leaking gasket and has no references to low boost pressure. HTH Scott