Chevrolet: 1996 GM SUBURBAN, throttle position sensor, good starting point

Question
MY SUBURBAN HAS 200,000 MILES ON IT,IT WILL DRIVE FINE FOR ABOUT 20 MINS THEN IT WILL START TO LOSE POWER, I WAS TOLD THAT IT MIGHT BE MY FUEL PUMP BUT IT START UP FINE AND IT DOESN'T SHUT COMPLETELY OFF WHEN IM DRIVING IT KIND OF SPUTTERS ANY IDEAS

Answer
James,
     First I would check the fuel filter. Once that is replaced if there is no improvement, I would have the injectors bench tested. If they check out okay, I would move to the Throttle Position Sensor. It would help as well to have the codes in the computer pulled to see if there are any stored. An AutoZone or another major chain store could probably do it free or for a small charge. That could give you a good starting point as well. I would think it probably is not the fuel pump, as when they go, they tend to not work at all. Check out these tings and let me know what you come up with. I had a similar thread with another guy a while back and we narrowed it down fairly quickly. Good Luck!