I have a 1992 Land Rover Range Rover. A couple of weeks ago, I filled the gas tank and shortly after, the engine started to surge. I was afraid to drive it until I could have someone look at it. Then, my "mechanic" brother-in-law suggested I replace the fuel filter. I have started driving it again, simply because it is my only transportation.We did that, but the surging continues. I was wondering what could possibly be the problem. Thanks for your help.