If you find low fuel flow after test, this is the last place everyone looks , but it should be the First, specially with an older car...

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=23I0RAMEE24D175GSB&year=1988&make=MB&model=560-SEL-001&category=E&part=Fuel+Screen