Lexx pipe jetting

Hi guys I'm fairly new to the atv scene. I've got a 2005 400ex and I have installed a new lexx slip-on with uni filter. I am undecided on if I will run the air box lid on or off. I picked up a new 42 pilot jet but I am not sure what I should use for the main or where to set my air/fuel screw.i am using keihin jets if it makes any difference . I found that my needle does not have adjustable notches on it. Can I get this thing to run good without an adjustable needle or do I need to pick one up? If I need to get a new needle will any model years work? I live in wi by the il border Maybe some of you local guys can give some feedback on my jetting questions and also whether I should run lid on or off.