Surges on and off with steady throttle & steady speed, usually most of the time around 6k rpm. If i do a pull or steady increase in speed it's fine & has no issues, only when i'm cruising it acts like the valves close and slows down for 2 seconds then jolts me and goes back to normal. When i bought it, it did have bad rust in the tank and had to replace the fuel pump. Any suggestions?