The 330 has 2" pipe, but I'm not sure about the 325. I would assume it's the same, but don't take my word on that. As far as the sound goes. The 330 with the valve disabled has a drone to it to begin with. From inside the cabin, all I can tell is that the drone is slightly deeper, but not really any louder. Hopefully this weekend I can can get someone to drive it down the street so I can listen from outside. Also, I'll try to get some sound clips next week.
Also, there is a counterweight that was welded to the top of the resonator. They cut mine off and welded it back to the pipes themselves. I'm not sure how it would do leaving this out alltogether.