Have you considered an exaust restriction?
10mpg sounds a little extreem for a fuel mixture problem... but you could take a look at the duty cycle with a milti-meter: http://www.landiss.com/mixture.htm

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/showpost.php?p=831799&postcount=13
http://www.peachparts.com/shopforum/showpost.php?p=831807&postcount=14