I bought one last summer, the hi-flow from summit, thinking my cat was plugged. Didnt feel any difference on the "butt dyno". Had it on for about 100 miles and put the THDP on instead. Up for sale if your interested.
Dunno about that, I have one on my Camaro for emissions sake and I noticed a difference in sound, it was much louder with the Cat Co on. I like it on the Camaro, I would say it does help unchoke alot b/c it is much smaller than stock and it does not look as restrictive. I got mine from Summit also and thought it was gonna be cheeper but I had to spend close to $150 for mine, they get you in the "starting at" prices. Of course the GN does not know what a converter is