Motor Saver all the way boyz. If you need even more filtration for off-roading you can upgrade to a three stage setup with the external foam. The Motor saver also acts like an air intake to an extent with the LARGE volume it brings into the engine and you may have to richen it up some.
I use OS's 21 filter on my maxx. seems to keep it clean with a lot of air flow. Granted, it did come with the engine. But i do like it. Has a screw in the top that you can easily make a hanger for.