Volvo Repair: Volvo CEL - Fuel Consumption, hand vacuum pump, fuel consumption

Question
I just bought a 1990 760 turbo that runs strong fine apart from a cel light and terrible - 10mpg - fuel consumption. Checking the engine diagnostics shows error 121 , 231, 232. Checking the spark plugs shows that i am running lean. Physically the AMM (MAF) looks great and the wire (s) are still intact. I am led to believe that the egr is faulty and has fouled the o2 sensor which would explain the error codes 231 and 232. AM i correct in this assumption? HOw can i be running lean and have high fuel consumption? THanks for any help

Answer
Kevin, Those cars didnt get the best milage anyway but 10 is a bit excessive.  The Air mass meter is probably working within specs but I have seen them with terrible milage.  you are correct on your assumption but usually what goes bad on those egr's is just the little thermal sensor.  I would test the EGR before replacing it.  You can check it with a hand vacuum pump.  hows the exhaust flow?  Roger