dual exhaust

I read a post the other day where someone said that a dual exhaust lowers your gas mileage...why would it do that? And does that also mean it hurts preformance?

somebody told me that i shouldn't get dual exhaust on my V6 because my gas mileage would drop a lot and it wasn't good for the truck. i also would like to know if this is true or not...does anyone have an answer??

never changed my fuel mileage.

1988 Sliverado 350/700r4....True duals from mainfold back, straight out the underside of the bumper. 4x24" tips. LOUD AS HELL!!!

The police really love it....good thing i'm on the police dept as a reserve! :)