Dyno results with flowmaster 50 delta

I'm trying to decide between two different cat back systems. I'm not really interested in sound (don't get me wrong - it's cool) as much as I'm interested in added horsepower. My wife and I each drive a '98 XJ and need to tow ~3000 lbs behind each of us from Massachusetts to Alaska. If you go to the following link, you can see the HP and torque increases with using the Dynomax Super Turbo because they used a dyno and tested the results. Has anybody evey tested their Flowmaster 50 Delta series with before/after results on a dyno?? Thanks.

Joe

http://www.rockcrawler.com/techreports/dynomax_xj/index.asp