My 91 740's A/C airflow diminishes during acceleration to almost nothing around 3500 RPM. Sometimes it gets to the point to where the engine too wont accelerate the car anymore instead just down shifting and making more noise. If I back off substantially and allow it to 'gather itself' the airflow comes back and I can resume the acceleration to highway speed if not more slowly. During the winter, i.e. not using the A/C, the idle suddenly dropped off and after several searches never found anything wrong and resorted to simply adjusting the idle stop. Now, with the fan on, I consistenly get the airflow dropping off.

Thanks for any advice.