My brake booster has a vacum leak. I would like to know if this could be the cause for my crappy idle and cel code 14 which is malfunctioning IACV. I have searched and not found any information on this. I have also cleaned the IACV and switched it out with three known working ones. And i have adjusted the FITV.

 

any vaccum leak is bad no matter where it is.

Try disconnecting the booster line and then plugging it completely so you can take the effects of the leaking booster out of the equation. Start your engine and see if the idle cleans up (resetting the ECU first is advisable). Don't drive the car like this of course - no booster makes brakes hard to actuate and dangerous.