94 Olds 3800 stalling, check engine light

94 Olds 88 3800 has been intermittently setting check engine light and stalling when cold. The problem has gotten worse and it will hardly start anymore. It either runs for a while and cuts out or at times. Today it was almost 60 degrees and it ran for a while, stalled and won't restart. When she does run, she runs like a top so I doubt it's mechanical. I've done the following with no improvement:
1) pulled the throttle body and replaced rtv coolant gasket which was leaking.
2) replaced spark plugs and O2 sensor - both looked pretty clean.
3) replaced coolant sensor in radiator.
4) replaced coolant temp sensor below throttle body.
5) replaced temp sensor in air filter box.
6) replaced fuel filter 4 months back. Any help much appreciated!