Loud, yes, but high maintenance. Filter element has to be changed often and there has been cases of the element being sucked into the intake manifold (it was waaayyy overdue for a change though, so it's not entirely HKS' fault)
I kinda agree with s15 too, the filteration isn't that good. There's just too many little holes in between the element and the bottom part of the filter. It looks n sounds damn good though, I can tell u that.
Friend of mine is using mine now, he's super happy with the power increase... =)