My 87 350 TBI will start up fine and idle normal for a few minutes or seconds depending on how warm the engine is. (Seconds if engine is warmed up.) But then it seems like after the initial high idle the engine will decrease in RPM's and then spit and sputter and eventually stall out. The SES code says HIGH TPS voltage. I just replaced it. It said LOW TPS voltage before i replaced it. Is there a way i can adjust the sensor?