Resetting the ECU won't do anything for the noise level, but should improve your fuel economy. Since the system's dynamics are different, ECU needs to re-learn. So resetting just speeds up the process.
As far as noise levels, I too got the "quiet" version of Brullen's cat-back. It's louder than I expected. I just recently installed Brullen's headers as well, so I have the complete Brullen exhaust package. Overall, the sound is much quieter than with just the cat-back. And you definately feel the difference in the performance! WOW!
The only complaint I have right now, is Brullen screwed up and didn't ship me a small electronics part that goes on the rear O2 sensor and I'm getting a CE light. The part was supposedly shipped over 4 weeks ago and I still haven't seen it! They supposedly re-shipped it again last week, so we'll see if this one turns up. So right now, I'm happy with the product, not too happy with the service. :curse:
Slim,