I've been noticing that my car seems to shake/vibrate when i come to stops. i thought it was a bad gas issue sence it only happened sometimes, and when it was real low. Well now that i have installed my new header i can tell its not that. I think it might be an idleing prob. but not sure. It idles at 500 and just a little below so maybe...490/495. Is this a normal idle or do i need to be doing something. Today before work, i checked the IACV to see if it was dirty and it wasn't. So i turned the little idle screw and nothing really happened. It just stayed the same with turning it both ways. Also i noticed when slowing down to come to a stop, the tech. kinda jumps from 1000-1025/1500rpms then back down.