to my knowledge it does not affect emissions at all. if you put a drop in filter and take the cover off the air box you will notice a sound diff. at WOT. after porting the MAF i immediatly noticed that the throttle responce was much more responsive. To do the job right be sure to take out the "black box" and DO NOT touch the sensor. other than that just dont shave it off so much you go through the housing.