I have a Volant CAI. My thoughts on it... I've been told by a few people, that it filters GREAT. One of these people was the guy trying to sell me an aftermarket filter, once he knew what it was he said to not buy his (Amsoil) filters. Now for my complaint about it... I was less than impressed with the box/filter design. The filter is actually 1"+ WIDER than the opening on the box. Kind of a PITA. There's plenty of space around it, why they decided to do that is beyond me. Their videos of installations have some that the box is noticeably wider than the filter. And the intake tube is angled a little weird so if the clamp isn't on the filter in just the right place it will pop off as you're trying to tighten the clamp. It does look fairly nice under the hood though. :thumb:
With that being said, the filters are expensive. $100 or so. XDP (Xtreme Diesel Performace) has the BEST price on them that I've found. ($66)
When I changed the filter, the intake tube was a little oily, but I didn't notice/feel any dirt in it. Haven't checked the turbo yet.
If you have the K&N unit I'm thinking of, you can pull their filter off and replace it with a 6637 without a problem. When you're driving, the intake temp is almost the same with a CAI or open filter type.