I was going to suggest leaking intake boots. Had it happen to me before. I like Lornce's suggestion better. This photo with the 2 different valve covers kind of bothers me though. Very nice job. I like these kinds of builds where it looks fairly stock to the casual observer but if you look a while and talk to the builder you find that there are many well thought out tweaks. I predict you will enjoy this bike mucho. I know I would.