2002 Saturn L200 trouble accelerating up hills

2002 Saturn L200 has been having trouble accelerating up hills. The RPMs increase and the enginegets louder, but the car continues at the same speed until the road flattens out. I have used "Gum-out" and this has not helped. You can almost see the fuel gauge go down, I drove for approximately fifty miles and it took a quarter tank of gas. I would really appreciate your expertise. I thought it may be the catalytic converter, but not sure.