where does it say that?
quote from HPI - page 107
picture 9 - "airflow meters that have been 'de-screened', such as this VG30 unit, are often more prine to pulse problems due to their large cross-sectional surface area"
page 108
picture 11 - "you can see how much surface area of the airflow meter inlet the wire gauze takes up. Adding an extra "screen" then reduces the inlet size to the engine dramatically, and costs you power in the prcess. Don't do it!"