My 60 is running a little rough. The idle is fine and once I reach a cruising speed the only issue is an occasional engine "hick up". As I shift through the gears, I feel hisitation and sputtering however it is not consistent. I have replaced the plugs, cap and rotar, and new wires, air and fuel filter. What else chould I check? Could this be a fuel pump problem or a vaccum problem some where and if so, how do I detect the leak? Any help would be awsome.