Stryfox,

I don't know if you can patent a tube with an air filter, if you can, you would have to come up with some really creative writing. No my patent attorney and I came up with a request to be granted patents for it, as a whole system, (dimensions, placement, configuration, etc.) as well as my MAF Integrated housing "Y" Connector, and also the support clamps and brackets. We submitted about 50 drawings, a black and white photos.
K&N couldn't sue me, because I'm not crossing any lines that they have drawn. K&N patented their filters, and trademarked their names on the intakes they produce. K&N couldn't possibly patent every product produced, they develop about 170 new products a year. Besides, they don't have to own everything that they come up with. Their probably the number one largest company in the aftermarket air cleaner/ air induction market. They have had such a successful history. So now they can just be a trendsetter and not worry about owning everything they come up with. I know if they come up with some sort of new technology, or go further into the world of Air Induction, like throttle bodies, or manifolds... then they will for sure patent those products.
So it was imperative to submit a request for a patent in design. Because other wise any one of the few companies that is willing to touch a Mercedes Benz could steel the design. And I would have wasted a whole lot of time and spent way, way to much money on designing an intake for just myself.
Good Luck on your intake Stryfox. If your going to do it the right way, then yes, you will have your work cut out for you. If you love doing it, then all the time you put into it will be less painful. I know, I did countless all nighters, racking my brain on finding the best configuration I could. From bends to accessories added to, every filter type out there. Have fun, and good luck man.