Ok this one has me getting fiesty. A buddys 88 K5 Jimmy 350 TBI has a weird up and down engine rev. Its ok at start up, when we get around the operating temp. the engine will go up and down at 20-35 mph. Sounds like a starve on gas, I put more throttle it goes away. The trans. is switching gears and have no problems going up or down a gear. Help us out please?!?!?!?!?!?!?!