Just to add to what others have said, the needle valve alters the output of the CO2. The operating pressure comes from the FE.
Incidently, I changed my FE over last night and couldn't get the gas to come out of the UP Atomizer even though the valve was still open as much as before.
I only get pearling on my HM, which, like Superman said, makes me think that either there is not as much flow to the HM as the other plants or that the HM is the only plant getting enough of the goodies. I assume the first as all my plants are growing well :thumbup: