stock mass air-flow sensor.
 

On my 1994 stock Mass airflow sensor it has a screen covering the whole. What is the screen for. Is it important or if I remove it will I gain power. I see that after markets do not seem to have the screen. Also can you do anything to the stock one like boring it to allow more air in?

It is to prevent foreign material from entering the engine. I would leave it in place.

You cannot remove it without it affecting the actual metering of the air (throws calibration off). Nor can you bore it out, without re-flowing and recalibrating it.

i also read that it straightens the airflow out and eliminates turbulence. its been proven that removing the screen actually hurts performance

my screen is removed and my stock mas is honed , and it does not not affect performance in a negative way . it is ok to do as long as you have proper filtration of the air entering the engine , the purpose of the screen is to protect the tiny wires inside of it which measure voltage. the turbulence is not necesary because the sensor does not measure air frequency like some mas's do. electricity travels through the wires which heats them up and the incoming air cools it down , the more air that hits it , the cooler it gets , and more fuel is put into the engine . i also datalog my runs and i did not notice a difference in air fuel ratio . you can hurt your afr if you move your mas to a different location , or turn it . just my 2 cents .

MAF screen
 

I have an 89 gt that ran a best of 9.10 @ 75.16mph on an 1/8 mile with the screen in. I decided to remove the screen and then
ran a best of 9.06 @ 75.86. I was very pleased with this mod. as I picked up a little e.t. and mph.