The Debate is STILL going on. Over at Contour.org every one swears on the KKM, but there are quite a few untested intakes. The Injen, the new Roar. I'd go over there and do a search and you'll get more than an ear full.
Personally I just 'tweaked' my airbox and have a KN and am happy with it.
I like my KKM because it was pretty easy to install and uses the cold air port.
I think the Ingen would be the best option because of its smooth long inlet tube, but it does not use the cold air box???
I have a KKM. It sounds really good with stock exhaust but with my Bassani I cant even notice it.
A few things I noticed with the KKM.
1. Worse gas mileage. Now, I am not blaming the KKM. It might be cause I was driving more agressively but the mileage went down.
2. Alot of heat gets into it from the engine since it is an ope filter. This loose HP but not sure the exact numbers.
I am thinking of building an airbox/heat shield for it, but I also think I might put the stocker back on with an K&N.