A stock GM MAF has two screens in series in front of the circuit board. Removing one may give a little more performance, removing both, without a chip specifically calibrated for no screens can screw up the idle and off idle characteristics.
Stock GM MAF's are too valuable to be messing with them. Leave them stock and upgrade to a new style LS1 or LT1 MAF and a translator. You can remove the screen from these with no ill effects. Screen removal is worth an additional 90-100 CFM for a 3" LT1 Impala MAF. blending in the screen ridge increases the difference to more than 100 CFM.
