With that fuel economy and the lack of power, I'd say you could be running a tad lean. I'd have the lambda tester out seeing if I could adjust it to the 40% mark or so.
Be sure that the bowden cable is adjusted properly.
1991 GMC Syclone
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM