RPM Drop at Idle

[WhaJac]

I did some searching but didn't find any relative information to my particular issue. 2008 2.5 sedan w/CVT. Just turned 3 years old and has about 70K on the OD. Injen WAI, and the K&N is cleaned twice a year.

Issue: When I come to a stop at a traffic light and after about 7 to 10 seconds, the idle drops about 100 RPM. Everytime, I look at the tach as a reaction to thinking that the car has stalled out. Once it drops, within 5 seconds, it's back up to normal RPM. It happens almost every time for about the last year. It started about 1.5 years after I put on the Injen, so I kind of ruled that out. I installed a new battery thinking that might help and I didn't want to get stranded, the new battery didn't eliminate the problem either.

So, I thought I'd ask to see if anyone else has an issue like this and has found a fix.
Thanks for your input!