help with multi meter readings on sensors

[modmonster]

either my MAF sensor or my lambda sensor is broken -according to the vauxhall forum. symptoms are lack of power. i have found the data sheet for both sensors, they are both bosch. i attached meters to both sensors. they both seem to be within working parameters!

the lambda sensor jumps around between lean and rich, alrhough is mostly lean 99% of time <0.03v. the air flow sensor (MAF) is giving low valves acording to my calculations. at 60mph the reading should be 2.8v for 13miles/litre. now i'm getting 2.8v only under maximum load, (up hill, top speed).

i'm thinking that the MAF sensor has lost calibration and is falsely telling the ECU that there is low air flow when in reality there is plenty air flow. the ECU then reduces fuel flow to compensate and ends up causing a mixture too lean. does this explanation fit the observations?