940 Non-turbo

Gas consumption is pretty high, something like 16-17 mpg. Used to be about 22 mpg for city driving.

Changed fpr and also O2 sensor.
Did not achieve significant improvement.

I've read that AMM failure can cause high fuel consumption rate, but at 30% less?

Also archives suggested that the temp sensor could also be a suspect but since the tail pipe is clean without carbon or oil stain, and couple by the fact that there is no surge in rpm above 1000, I suppose this rules out the temp sensor.

Have also tested the injector for leaks and found them okay. Again injectors ruled out.

In addition I occassionally experience slight stumble when braking to a stop on a uphill motion with slight rpm wavering between 500-900 for may a couple of seconds but not enough to stall the vehicle. Also observed that when cold, car would stumble and struggle to move on from a start position. This probably last about 5 seconds.

So, is the AMM the missing link? Had to change this one if it is not the cause.

Thanks for all your advice and suggestions.

Laozong