Jorgen,
Personally, I think it's the threads between the main body and the "actuator" sleeve. The needle itself is fine, and there are no O-rings to go bad (that is the one VERY cool thing about the CMD unit, they have a teflon sleeve with a snug fit on the needle). It's just the threads on the black plastic piece start to wear and the overall fit gets loose. I did see one CMD needle that had the side nipple come completely off and it appeared to have been GLUED IN!.
I have a BV needle in a 60 boat that I scratch-built, but it's not a very good design, and I haven't ran it much since it's maiden voyage, so I really can't give you any reliable input on the needle. I can tell you that with as well as the OS unit works, I probably won't be trying any BV or CMD needles until I have reason to.
Thanks. Brad.
Titan Racing Components