hi folks. every time i fill the tank on my rex x thre car seems to run slowly for the first 1/2 of the thank then it runs ok except it strugels for power a bit when takeing off especially on grass. also i have to leave the throttle barrel open more than 1/16" or it cuts out if left idleing for a while. the car is fairly new only about 2 gallons through it so far. woulkd be greatful for any help as im new to this game. this is my first car. would love to ge it running spot on. thanks.