sc300man

You hit the nail on the head with this one. My old MKIII supra had a very, very similar VAF (although Supra guys call it an AFM, Air Flow Meter). In fact, your VAF is a popular upgrade, due to it being bigger, for our AFM. Anyway, the screen is there to straighten out the air before being metered by the sensor. I personally know about a dozen people who removed the screen, myself included, and noticed the same problems you encountered. In all cases, when the screen was reinststalled, the problems went away. As for freeing up some airflow/HP. I know of one guy who dynoed with and without the screen with no difference at all. As you have figured out, just leave it in. Josh