I would like to say "yes" for certain, but I can only use the seat of the pants dyno. My before dyno had the crush bent system. 165hp. My most recent dyno I added the mandrel bent system, catco cat, and the ProM MAF. 171hp. The ProM was added at the beginning of the summer, the new exhaust and cat added at the end of the summer. So, I didn't dyno the exhaust gains, but rather all my summer mods' gains. The new exhaust does feel like it has a little more up top, though (again, only seat of the pants testing).
I must say, though, that I'm so pleased w/ my exhaust setup. I know it flows well, and it's soooo much quieter inside.
Plus, as the new mufflers get broken in...they sound cooler and cooler.
