I just setup an XP2 on my 29g and at first it was really noisy and sounded like a HOB
does when its trying to take in more water...it would do that ever few minutes. I watched the tubing and found that large air bubbles were going into the filter. I moved the intake tubing around to kind of straighten it out and it still did that. But, after a couple days it is now quiet like my others.
Have you tried moving the tubing around a bit (obviously you can't move it much...)?
What all media do you have in it? Sometimes when I would put too much in my XP3s they would be noisy.
Sorry I can't be of more help.