i have an 87 silverado with a 350tbi and every once in a while especially if i have been sitting idling for a while or just start the truck, if im turning even a little and idleing the rpms will dive and today it died on me. also...it kind of hesitates and surges if im trying to feather the throttle..but runs great if i get on it...but just taking off slow it will surge and hesitate. any ideas?