rough idle

I have started to have a rough idle on my 1989 2.5 liter Sonoma. I have cleaned the idle control valve, and replaced the throttle position sensor. I still have a problem when I shift from Park to Reverse. As soon as I start moving the gear selector, frequently the engine starts to stumble, miss, and many times quits altogether. Does anyone have any ideas?

Check all your vaccume hoses for dryrot and cracks... Did you spray and clean the throttle body blade? How are your plugs/cap/rotor/wires?