1990 Celebrity Start and Idle problem

I have a 1990 Chevy Celebrity wagon with a 3.1 liter V6 which has 178 Kmiles on it. On occasion, it will be difficult to start. When it does start, it stalls when I release the gas pedal. It starts easier when warm but will still die when the pedal is released. By holding the pedal down a bit, I can keep it running and drive it. When driving, the engine power seems normal. Then, usually after shutting it off and restarting it, the engine will idle normally as if nothing had happened. This is an intermittent problem…most of the time the car starts easily, even after sitting for weeks. As far as I know, all of the sensors, the EGR valve and the timing chain and sprockets are original. Where do I start?

http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152800cc319

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Tester