I'm no troll either and I agree that aftermarket exhaust does not add power. This has been the case with all the cars I've owned that had aftermarket exhausts.

If we were adding serious horsepower mods. (like forced induction) then our OEM exhaust could become a restriction.

As for dyno results, they are typically not accurate. Dynos need to be maintained and kept in manuf. specs. I suspect the majority of speed shops don't bother to keep up with this. You can also play games with SAE vs. STD correction. It's done all the time, it's called "marketing".