[cstreit]

I suspect what you are seeing is just the accelerator pump pushing gas through. On the Weber IDA's any time you move the throttle linkage gas shoots from the aux venturi as the accelerator pump diaphram is pushed.

Try doing the same thing with the car off. I think you'll see that it's not the airflow/mains. The only way to really diagnose this is with a wideband O2 sensor.

Let me know.