Engine starts well when hot, but wants to die for a moment.

Hello. I just had a new PCM installed in my car, and it runs, and starts great. However when the engine is warm, and left for a few minutes, it starts up fine, but RPM's drop to almost zero for a second before going to normal. With the A/C on, the engine will die after starting when warm, and I have to try a couple of times to get it to start, and if I turn the A/C off, then it does start, but with the immediate low RPM, and almost dying for a second. Car did this before I had a new PCM installed, and was worse before the new PCM was installed. (PCM was "fried" and that's why I needed a new one. No signal at all when trying to use a scan tool before new PCM, and car would crank over, but not start before new PCM.) Any suggestions? Thank you.