I have not tried the Big Gun but I have a Graydon Proline Big Bore pipe on my 400EX and love it. It is very strong on the bottom end and pulls real hard through mid as well as top end. Check out there web site at http://www.graydonproline.com/ Ask for Darryl he is always more than helpful to me with any questions that I have. Tell him Kevin Haynes told you to call him. I promise you there pipe and service is second to none!
Thanks for the advice,,,, but I just orderd the big gun yesterday. So, hopefully it gives me some more bottom end and midrange that I am looking for. I went for the quiet core, and spark arestor, Kind of pricy, but what the heck.