my car doesnt handle deceleration properly, or engine load correctly, the AC, power steering, and when i switch on and off the headlights, at idle all of these things make my rpms plummet to 450..especially when i turn the wheel while im stationary...what is causing this? i have no vac leak btw...had one found it and its fixed, could this be my IAC i already cleaned it....or bad alt? im lost and frustrated

btw i have no codes....only the ones from my egr and rear o2 delete...