Hi I put a 583 into a 94 470 mxzx. It will start but it won't stay running for more than 30 sec and it needs to be full throttle and still runs like shit. I have completely cleaned both carbs fresh fuel, new fuel lines, fuel pump and fresh spark plugs. I have primed some of the coolant lines, have 145 compression in both sides have tried adjusting the idle screw numerous times doesnt improve or get worse. I am pretty good with sleds but I am stumped.