I think there is a lot of hype about the K&N but, I run it on my car and have for a few years. I really didn't see any performance change but, when you have so much HP you probably would not feel any difference or a change in your ET. My 04 runs 11.55 @121 mph but I don't really think it's much more than being a good driver with good launches and consistant shifting at the right moment. I think most of the bolt on stuff in front of the clutch has a lot to be desired. I actually think it's what's behind it is where it counts. A solid clutch designed for racing, strong half shafts, OS Giken LSD differential with some strong dana gears, ad some lightweight SSR 18" rims wrapped in M&H Racemasters and you got something you can get nasty with. I don't have headers but, have given some thought of adding but, not much bang for the buck. I have a mail in DC tune, which that even didn't give me much in the HP area maybe 15 ofr 18 HP but it did help the whole engine run smoother. I had the manifold ported but, again only so much you can do with an 04 manifold. I had always thought that the 04 top should be removable to access the castings on the inside. Low and behold the gen 4 finally did that. I am sure it's better than mine but mine works ok. Again nothing to write home about. When I first started to run the drag strip I was runing in the low to mid 12 second range but with practice, a launch light and shift light, and the items listed above and a PLX Tach which I can read the digital numbers it becomes very easy to read.
