MBRP makes nice diesel exhaust systems too. I have one of their 4" straight pipe systems on my '01 Cummins and love it. Easy to install, fits great, and sounds good.
You really need to be making a lot of power to need a 5" exhaust system over the more common 4".
I agree w/ the K&N comments too. Don't waste your money.
I have the aluminized on mine, looks brand new except the bend behind the axle had a hole after 4 or so years. Other than that, it has been a great system. Maybe too loud at times, but does sound good.
