Evening Dick,

I assume the filter was fitted to try and cure the problem. I would expect to see a similar trace to that of the Bosch hot wire variant. Now to confuse things... I would expect to see a higher voltage than 3.8/4.0 volts maybe up to about 4.5v. However the AFM will only record the amount of air passing through it so if the throttle was wide open and there some other fault with the vehicle such as blocked exhaust etc, you won't get a max reading from the AFM. So a low reading on an AFM could be a sympton..rather than the cause.

The fact that the O2 sensor does not go rich when you blip the throttle also indicates an AFM problem...assuming everything else checks out ok.

Regards

Pete M