yes it makes it run leaner. all it does is trick the PCM into thinking there is less air coming in thus it puts more timing than it would normally. yes it makes a few rwhp IF done correctly. i would buy a set of MAF ends before i even thought about touching the MAF housing siince the MAF sensor is ULTRA sensitive. if you touch the little sensors there is a a good chance of you destroying it. they are damn expensive. i have seen the plastic aftermarket ends go for 30 dollars or cheaper used. if you are automatic car DO NOT FUCKING DO IT!! on auto cars it spikes the line pressure because the line pressure is related to MAF volatage. tranny will be shot fast.

also, why do you think your car is running WAY rich?