Hey that's what I have been reading about PVC valves and combustion chambers...Do you think it would be OK to leave the draft tube working ( when I find one) and a breather cap on the valve cover and a paper type air cleaner set up? Or should I leave oil bath air cleaner hooked to the valve cover an no paper air cleaner? Also one post said PVC are better as the guy gets oil on his clutch from the draft tube....I think Chevy would have figured that one out when they built them? THANKS, Steve