No, the stock intake plumbing has no such 2.5 restriction unless it is the snorkle, I'll save Qwik the trip in here.
The K and N is badass because of the sound, thats it. It actually holds heat more than the stock plastic, however I have one and have had no issues after 3 yrs.
Mods: ZZP stage 3, 2.9 pulley, prefab pcm, 60lbers, AEM gauges, KandN CAI, SPEC stage 3+, ZZP S3 heat exchanger
ZZP long tube header, Strut bar, ZZP rear mount, Progress rear sway bar, Redline Tuning hood struts freshly installed.