Odd, it's understandable because the car is in gear on decel usually. So it's trying to idle around 650rpm. Which can be tough depending on the cam. Then add the stress of AC and PS to the idle heading down. That's the typical issue. Bump a little takes care of that.

however Brandon, with you.. we know you might come up with some really oddball issue that we'll have a heck of a time figuring out.