My mule was running fine until I replaced the fuel pump and then the idle became erratic. When I first crank it idles slow but the rpm goes up and down like it wants to die. I reave the engine and let off and it runs idles perfect but when I drive off no matter how fast or slow when I stop the idle is slow again and acts like it wants to die and while stopped I can reave it up and let off and it will run perfect again. Any suggestions on what may be going on? All advice is appreciated.