Ok, my brother has a 1997 Chevy K1500 Silverado with a 350 TBI engine and auto trans. When driving along at highway speeds, the engine sputters and basicly runs like crap. If you floor it, it straightens out somewhat, bit it still sputters just a bit. The SES light also comes on and flashes steday for a few seconds, then goes out. it repeats this constantly. He already has installed new plugs and wires, and his air filter and fuel filter are good. What could be causing this? I'm thinking maybe the throttle position sensor or maybe an oxegen sensor. Any input on this would be greatly appreciated. Thanks Jack.