Re: exhaust again?
I prefer to keep the emissions control systems in working order, so I still have the cat and dpf on my '07. However, when I put the 3" MBRP kit on, I did get better economy and smoother sifting. My wife really noticed it, but did not object to it being a bit louder.
The factory exhaust on the WK CRD is actually pretty good, so improvements are subtle.
the GDE Eco Tune was by far the biggest upgrade, but the MBRP exhaust is visible and adds a nice touch