I just noticed that Im missing a rubber cover for my Idle adjuster do I need that? Dose it stablize my setting?

I might be using the wrong terminology so heres a pic:



If y'all can't see the pic just click on it to see a larger view, I circled it in yellow.

FYI not my car in the pic.

 

No reason to mess with it unless you have idle problems. Then if you do, follow the steps in the FSM for idle adjustment.
*edit* The rubber cap is just there to cover the adjustment screw, does not stabilize the adjustment.

 

AH I see. Ok thanks, I was worried that the screw could rotate due to vibration and mess up my Idle.