When I go from park to drive at halfway or full temps the engine RPM will drop to 300-400 for a second, almost on the point of stalling, sometimes it will, however after a second it will go back up to close to normal idle it seems. It seems it is getting worse at below freezing temps

Any ideas on what would cause this?

I have replaced most of the ignition components recently. Cleaned the MAF, etc.

94 L27 3800 btw

When you say full temps.. do you mean up to temp or overheating?

Also any idling issues or odd other things?