Obviously not pegging out on the MAF then at about 4.6 volts. Does the voltage change at higher rpm and have you got a bhp figure for your car?

On the 'COSY' code EEC-iv I've got the air transfer table shows the following for the top 4 entries (rounded to 2 decimal places):

Volts kg/hr

16v 737.75
5v 737.75
4.5v 526
4.25v 455.25

On a couple of Mondeo normally aspirated 2.0 litres ecu's I have the code out of the second row is 4.75 volts though. Top row always is 16 volts.

I don't think an error code for a MAF range error is thrown out unless the voltage recorded is 15.3125 as the ecu code shows the maximum A-D counts for the MAF as 62720 ( / 4096 to get volts).

Sorry to get off topic from your original problem, but it's useful to see what changes the ecu can cope with.