Whenever my tank gets below a half, at around 3500 to 4000 rpm, the engine seems to rev down and almost stop, then the car will jerk a little bit like it is out of fuel. Sometimes when I shift up a gear it will go away but other times I have to shift up 2 or even 3 gears to make the car run normal. I thought it might be the fuel sending unit or sediment in the tank, but I am not sure.
