Actually, dual exhaust when properly done, does NOT lose power. Also, dual exhaust does not always mean louder either, so both of those statements are incorrect. I personally wanted dual exhaust becuase of the looks, it simply looks better, but that is personal preference.

 

Yeah I think it might have something to do with the dual outlets. I also have a SI/SO Super 40 muffler and it sounds great with no notivcable loss of power IMO. Not to loud but definatly beefy and deeper tone than alot of other trucks ive heard on the streets.
Also to mention, since I installed my Troyer tuned xCal, the exhaust tone changed significatly and sounds even more intimidating now.