hello and merry christmas, when my car has less than a 1/2 a tank of gas, when i drive it and come to a red light or stop the rpm's seem to drop to about 500 then kick back up to the normal 1100. it almost stalls.when i fill the car up with gas it runs perfect. what is this?

 

hmmm...I'd say fuel pump but maybe sombody else will chime in on this.