2004 Dodge Stratus Rough Idle

I have a 2004 Dodge Stratus SXT Sedan that has recently been giving me issues with rough idleing.

Description: The car will run fine on the highway or long drives. However many times when I am sitting at a traffic light I can see notice the car appear to want to stall and the RPMs drop. Sometimes this happens only one time. Other it occures about three or four times. I have had this issue at times when I have started my car up in the morning and let it warm up (since it is now winter). The other day when I put the car in reverse and backed out of a parking space the car was running rough and stalled. I was able to start the car up and had no other issues at the time.

Work done: I had the car at three different shops. Back in October I had a general tuneup done on the car and had the spark plugs replaced. I had the issue with the rough idleing prior to this. The issue kept getting worse and around the end of November I took it back to the dealer (Dodge/Chrysler Dealer) to have them look at it. They told me that it appears to be carbon build up and suggested replacing the spark plugs and wires. I explained to them that I had the spark plugs done only a month ago. They told me that they found Platinum tip plugs in the car and only recommend gold plugs. They said the spark plugs are also misgapped and one of them was cracked. I had them do the throttle body clearning but took the spark plug issue back to the shop I had that work done at. The guys at the shop I had the spark plugs done said they are only able to get Platinum spark plugs and don't know if this is a dealer only part. They replaced the spark plugs and said they are gapped correctly. They also said they don't know why the dealer said you can not use the type of sparkplug in the car because it calls for this type. I drove around with the car for about another month and the same issues occured. It is now January and I had the car stall on me so I took it to another local shop who I have used before that seem to be good at troubleshooting very odd/difficult car problems. They kept the car for 2 days and said they ran several tests on it and the problem is with the Idle Air Control. They said the problem is not occurring all the time but replacing this should fix the issue. I had them do this and they said they tested the car after and it ran without any issue. I drove the car the next day and when I let it warm up in the morning and I was cleaning off the snow I could thought I could hear the car running rough twice but figured I was just parinoid. I drove the car to work (35 miles one way and didn't have any issues - 11 lights however this is morning driving so not as much traffice). When I came home and stopped at the first light the car ran rough again and could see the RPMs drop. It only happened one time coming home. I then went out again but took my family in the car because I wanted someone else to see the issue and know that I am not crazy. We drove the car in some locations that I had to sit in traffic and I pointed out three different times it happened and they noticed it as well.

Question: What should be looked at to try and resolve this problem.