I have a 98 STS and my SES throws the (P0101) MAS code just about everytime I accel up the on ramp on the freeway or any hill for that matter...when tirpped I feel a sudden Burst of power in my acceliration... which is good and it doesn't feel like its a boggy any more.... Also i have observed that it shifts harder and from a dead stop, it takes off quick as hell as compare to when the SES is not tripped.

Why does it act this way is it dirty or do I need a new one? If its just dirty, how do I clean it? If not where is a good place to get a new one for a good price.. Also I have changed the air filter its just a cheapy Fram Im gonna get a K&N next week...Also what is the screen for on the MAS? can I take it off or is it better to leave it on?

It sounds like the MAFS has failed or has a problem with the wiring connections to it. You can try cleaning it. Try hosing it with starting fluid (ether). That will rinse any contaminants off it and wont hurt it. Take the MAFS out of the system and hold it upright and just flush the starting fluid through it from a spray can. Forget the K&N. Save your money and just buy fresh paper air filters occasionally. Leave the screen in. It improves the signal the MAFS generates by straightening the air flow so the sensor sees cleaner air flow for a more accurate signal.