air intake resonator
 

hi could anyone explain what this does and why i should keep it

i got a 1999 chevy cavalier z24 with 2.4 dual cam engine with a rough idle and it seems to run perfectly without the air intake resonator on so if i put a direct connection from air box to intake would that be safe also if i take it in to aircare will i fail without that part attached

With a properly designed air intake resonator, it is suppose to help you dampen the pressure wave harmonics when the intake valve closes -- that is its primary job. If you remove it, you would likely hamper the effectiveness of your entire air intake system by resulting in some worse airflow.

Long story short -- I wouldn't take it out unless I am replacing it with a known aftermarket part that has been tested to show overall improvement in flow and hp/tq numbers.