yah make sure the washer around the tip of the spark plug isnt damaged, if u have any crud (dirt, debris) on the tip of the threads itll make it so u'll lose compression thru the spark plug chamber, and also check the ring gaskets at the top of the valve cover, with ur new vc gaskets you'll probably solve the problem, and its good to use a few dabs of rtv silicon around the edges of the gaskets also, which i always do just to help the sealing process.