What is a MAS honeycomb?

This refers to a thin, gold-colored grille material located at the front of the mass airflow sensor (MAS). Its reason for living is to 'straighten' out the incoming airflow into the MAS. This is a requirement of the Karmaan vortex airflow sensor used in the MAS. The upper portion of the honeycomb affects the measured air, while the lower portion affects bypass air - air that is not measured by the MAS.

Removing the lower portion of this honeycomb-like material can sometimes help delay fuel cut on 1G DSMs, by adding a few percent more unmetered air into the air/fuel mixture. Some owners, however, complain the mod makes their engine run rougher - the current theory is that the turbulet lower airflow somehow affects the non-turbulent upper airflow where the two flows meet.

Please note that under no circumstances can all of the honeycomb material be removed from the MAS. Doing this will screw up your idle huge, as the MAS airflow measurement gets all screwed up. Only the lower portion may be removed, and generally only on 1G cars.

2G owners often find out they can't remove any of the honeycomb material. Fortunately, since the 2G MAS flows a lot more air than the 1G MAS, the honeycombs should be considered far less of a concern.

You can read Jim McKenna's MAS modification for more information. For those interested in the entire MAS sensor assembly, please read Mike Jackson's DSM MAF Theories Page (Internet Archive)