Im having the same problem and I think it has to do with one of the exhaust valves. Im losing power and I have smoke coming out the valve cover and its exhaust. If you just have smoke then it may be a seal. Im not to sure but im taking mine apart today so I might be able to tell you more laater. And no there isnt supposed to be smoke coming out of the vent on the top regardless if its connected or not. The valve area is more of a small vaccum. No pressure or smoke should be coming out.