2001 Blazer Idle problem

Hi, I've searched through the forums a few times for idle problems, but I haven't found one that's exactly the same as mine, so I'll start a new thread.
Occasionally, when I come to a quick stop, whether in reverse, or at a stop light, the idle drops to about 200rpm then bounces up to 700rpm and back a few times before it levels out at 500-600 (which still seems a bit low), and a few times it has stalled. This problem just started happening this past winter when it was cold -10 to 20 degrees. Prior to this problem, I had the intake gasket and plenum gasket replaced. After that was done, I started having the idle problem, and the SES light came on a few times. I took it to AutoZone to read the codes. If I remember correctly, the 2 codes were 70 and 71 - Left Bank Lean and Right Bank Lean. The vehicle has 70k on it, and the fuel filter was replaced around 35k. I noticed several other threads relating to 'rough' idle problems, but mine just fluctuates at a stop - no misses or backfires.
It's been a while since the SES light was on, but I have a friend with a Snap-On diagnostic equipment, and I will try to get that done this weekend. Any help or suggestions are appreciated.

clean your IAC and make sure all the vacuum lines are attached where they should be.