2004 Dodge Neon Idle Irregularity

I've been troubleshooting this problem for 4 months now, I've checked the fuses for shorts disabled numerous systems, and have come up empty handed. I've also changed out my TPS, and IAC motor. The only mod I've put on the vehicle so far is a K&N air filter. The problem is everything runs perfect unless I'm pulling up to a red light. While I'm slowing down my idle flucuates until I come to a stop and then it gradually drops down to 500. At this time the entire car shakes just enough to notice a difference. In the same situation if I repeat these steps while I'm in neutral everything runs perfectly. There is no check engine light or indicators of vaccum leaks. Therefore the only time the problem shows up is when the vehicle is in drive. Do you have any other suggestions?