I think the ecu must only look at the peak. After all, that is the max airflow (Valleys are when the valves are closed). Furthermore, the ecu obviously thinks the airflow is off scale, since it's going so rich. Note also that all the peaks are around 5.2V, but the Valleys change. Has anyone identified this circuit in the ecu? modifying the circuit to look at the average or valley might be one way to trick the amm into being more useful for higher air flows. You can certainly flow allot more air through a 2 inch tube without being choked (super sonic) than an amm can measure. Even at idle, airflow through an amm it's turbulent according to Reynolds number calculations. I think intake velocities up to 36 psi of boost are still well below choked flow. Note that due to the hot wires small size, 70 um, flow around it is laminar even at really high velocities. Note: I amm not an expert it electronics our fluid dynamics, so my assumptions could be wrong.
1993 245 Classic
1992 245+T (DD) Build thread here.
1972 P1800E Chassis number 39412 (Doesn't exist according to Volvo)