This investigation was done to get some insight into the amount of obstruction the screening at the entrance to the MAF housing causes.
I had the ends from a stock MAF housing which I attached directly to the flowbench to measure the airflow through.
Running the test depression up to 10″ of H2O the results were:
The setup for the test was not ideal, just having the ends of the MAF housings and mounting them directly to the bench which meant the sharp edges were present for air to flow around as the air was drawn through the housing ends. But, as a check to see approximately how much obstruction the screen causes I believe this setup was adequate.
The removal of the screen under the conditions that I tested showed roughly a 5% increase in airflow at the same test depression.