G9 Questions

[biglug]

So I got my cart running and charging now, When I got it I noticed that the carburetor was not hooked to the air box so I hooked it up and then it would not run with out keeping the chock half way on. So I just unhooked it and drove 5 miles or so to make sure all my other fixes where working. 1 of the things I fixed was the valve cover was leaking oil bad so I cleaned it all up and put in a new gasket. When I stopped from the drive I noticed that there was oil all over it seams to be pushing up the crank breather hose. So I took out the air cleaner and hooked up the air box and it ran fine and seem to stop leaking oil. My questions is with the air box not hooked up is there no vacuum to the crank and is that why it was leaking oil out of the crank breather hose on the valve cover? Question #2 the air filter did not look bad but with it removed it ran fine so should I try a new air filter or look for something else?
Any help would be much appreciated