Today when i started my truck, it fired right up as usual but then the rpms went down to almost stalling before coming back up to normal. When i drive it, its fine. I also noticed that when i apply the gas while in park, the truck almost dies before coming back to idle. As i said, once i put it in drive and drive it, its fine. what could this be? I replaced my airfilter about 4000 miles ago also. THanks

anyone??????

Remove the TB and all the sensors attached to it and clean everything. If that doesn't help, replace the IAC first. Then the TPS.

Also, trace all the vacuum lines you can find to make sure there are no cracked, damaged, or loose lines. Common failure points are at the cruise control module up by the battery (lines can be eaten by battery corrosion), under the vehicle by the CAD, or by the firewall where the lines are split for the HVAC controls, cruise control, etc. I found a leak from a damaged metal line under my truck when I was troubleshooting an issue where my CAD would not want to disengage. It smoothed out my idle as well when I patched it.