Misfire 99 Tahoe when warm

I am trying to see if I can find a fix for this problem. I have a 99 Tahoe with 139k. When I start it up in the morning, the motor runs smooth and shifts great and no misfire is present. After driving around town for a while, there is a noticeable misfire when the truck is put in neutral. This misfire is not present all the time, mainly when it has warmed up. Sometimes worse than others. In the past year, I have installed new plugs, TPS, fuel filter, fuel pump, EGR valve and cleaned the MAF sensor. Not sure what I am missing to solve this problem. Any input would be greatly appreciated.