Roy,
I just replaced my Banks monster muffler with a Donaldson & can't believe the difference... I know it's a long way, but Stans headers in Auburn Wa. sells an aluminized kit with the Donaldson for $400. & they'll ship it to you ... I am getting 25. 7 MPG on the highway at 55 with the cruise set, & that's up . 7 since the new Muffler... The drone from the banks is gone & the exhaust tone is now lower & wayyyy quieter. . Sounds like a semi exhaust, but really quiet & healthier than any cummins I've ever heard (except straight stacked ofcourse)... The spool is way quicker, with less boost on specific grades/areas that I drive every day, which I believe tells me that the turbo doesn't need to work as hard because of the muffler... I also saw a fuel pressure increase of almost 2 psi... The Banks CFM was 800 or so & I think Stan told me the Donaldson flows at 2100... One comment about the silencer ring... I too took mine out & noticed a slight decrease in fuel economy & I didn't like the different sound either... I've been told by the Turbo Air Guide company, who apparently does flow studies) that the silencer ring has a second purpose, & that is to keep stray turbulence coming off the compressor from interferring with the intake flow... Basically redirecting toward the flow of the intake direction... I didn't believe it, but after seeing a difference in economy I do now... Call Stan & tell him what you have & he'll send you a bolt on that you'll be verrrrry happy with... That is if you don't want drone, you want faster spool up, & increased fuel economy/increased HP & torque... I do have the Banks 4" turbo exhaust body & 4" stainless all the way out with 5" tip behind the wheel, so I expect the Donaldson will have had a little better incresase for me, because my exhaust body has less restriction than your stock unit, but as I understand it, Stan's aluminized which bolts up to your stock down pipe will increase all that I've mentioned... If you aren't happy with it (which I'll bet money you will be) you could always go back to stock & sell it on ebay.
Call me if you want to shoot the bull... 856-404-8397
R/
Jim