I'm going to say NO, you don't need a new PCM. Idle issues, and issues of stalling while coming down from higher RPMs (coming to a stop light or sign) can be caused by other things.
- the IAC (idle air control) sensor could be gunked up or need replaced. This bolts onto the side of your throttle body. Easy to removed, clean up, and install.
- While you're at it, pull the throttle body and give it a good cleaning too
- How about your vacuum lines and their connections? The Fuel pressure relief valve vacuum line runs off manifold vacuum.
- Another possibility "might" be the temperature sensor that tells the computer how to set the fuel mixture (works like a choke sort of)
So don't give up hope yet. I bet it's something simple.
https://www.youtube.com/watch?v=_2VDYu5144k
https://www.youtube.com/watch?v=fpYSfvAxSkk
I personally like the 2nd video better because the girl explains things really well and you have to give her props for doing it in sub-freezing weather.