Guys, when I saw the photos of what Callaway Engineering did to their SSR, that "iced it" for me. They merely opened up the exisitng hood on the air filter box. No K&N cold air system. If they truly felt that they could have improved on this, then you know that they would have done so. I modified the hood of my air filter box, and you can feel and hear the difference. My truck feels like it pulls a bit stronger and longer.
Here's a link to some photos:
Modified Air Filter Box:
Admittedly, the K&N cold air system looks quite custom and very "racy". However, I'm a big fan of symmetry. Inherently, the air tube of the SSR is offset to the left in the engine bay, but the stock air filter box straightens out the look by being centered itself. The K&N cold air system accentuates that offset, unsymmetrical look. I did not like that. Also, I believe that engine bay heat is better sealed off with the stock configuration with the foam sealer of the '05-'06 SSRs. That big air gap around the air tube penetrating the back wall of the K&N system seems suspiciously very "un-cold air like" to me.
My $0.02 is modify (open up) the air filter box hood, get yourself a high performance air filter (K&N, Fram Air Hog, Amsoil, etc.) if you'd like. You'll get some improvement and save a lot of bucks for other mod's.
Alex