I want to put a duel exhaust on my truck but I'm not sure if I will lose torque

 

If the exhaust system is appropriately sized for the motor you shouldn't lose any TQ.. should actually gain some.

 

No it shouldn't If anything you'll gain some HP. This is the one I went with:
1987 - 1996 Ford F150 All AMT DOR/S [17471] - $498.90 : Flowmaster Inc. Exhaust Shop, Love That Sound! FORD F-150 V8&orig=17471

nice moderate sound and easy install

 

That there flowmaster exhaust is a pretty penny!

 

thats more than half what i paid for my custom duel exhaust (headers back WITH highflow cats!)

 

If you have a 4x4 (t-case n stuff) There is no advantage to a duel with all the extra bends in the piping. Stay large single. If its a 4x2 I say doittoit. You will like it over stock and see gains over loss. Same with a single good breathing aftermarket, as well.

 

I dont understand why people say true duals on a 4x4 is stupid or not practical. i JUST installed an exhaust on my buddys 5.0 and we ran both pipes to the pass. side, like stock. The only difference is that there was 2 pipes instead of going into one

 

I dont think its stupid or not practical. I think its said due to cost over performance gain's. I have duel on my F250 4x4 But if people don't want to pay the extra expense its said there is no need to. I don't think anyone on here has dyno-ed both to even tell. My statement above is made off the majority of this data base. I still did duels... and on the cheap! Also OP said cat back ... thats not duel and I dont see the point.

 

I agree with what everyone else has said. You should actually gain a little power with a cat back. I would just buy the muffler of your choosing and have an exhaust shop install it and route the tail pipes how you want them. You can even choose your tips then. If your truck still has the stock cats, a Flowmaster won't provied much sound at all. In my opinion, the only way to have a good sounding truck with stock cats is to run a torpedo pack glasspack or straight pipe behind the cats.