I just installed my hooker shorty headers and i noticed that after driving around with them and all my other mods that i have at a stop when it idles it will sit at 1000 rpm and SOMETIMES not all the time it will jump and float back down from 1000 to 1300 consistantly until i drive. is it my mods working against me? maybe not enough back pressure? maybe a sensor is off, but no service engine light? does this go away?

mods posted below in signature for an idea what iam workign with back pressure and air flow wise. any answer would help a lot thanks everyone