trac off - Stalling

My 99 Grand Prix stalls while driving. It happens about once a day and the check engine light is not on. The trac off light comes on shortly before the car just cuts off. I can be going 10 mph or 65 mph. Sometimes it starts right up and other times it takes about 15 minutes to start. I have changed the fuel filter, fuel pump reister, and the mass air flow sensor. Any ideas?

lets see you spend approx 500 dollars so far spend an extra 100 and go to the dealer have them scan the car for problems. Usually the trac off light only comes on because the engine has a problem and it disables the trac system to prevent problems. We could sit here all day guessing what parts to try next but it would end up cheaper to have your car scanned. With the added info from that it would make it easier to fix.