So I just installed the Kinetix V4, and I can really tell a difference up top, and you can really hear the engine resonate much more. I'm curious though, with my current setup, which includes AEM CAI, unorthodox crank/underdrive pulleys, stillen test pipes, stillen catback, kinetix V4, would I notice a big difference if I decided to install the 2005 track model lower plenum and/or plenum spacer?