I was actually gunna buy one of these til I found a cheaper one, they don't really increase power but they do give a nice sound, they certainly won't cause a loss of power.
i doubt there's anything wrong with them. They've probably done a deal with a filter supplier and just branded the product as there own. Alot of companies do this
They are just the cheap metal weave type with no cotton/ oil. they work well enough when fitted correctly. They just have max power stamped on the top.