I have a 01 f150 w/5.4 that has a stock muffler with "T" out of it for duel exhaust. I like the sound, but am afraid that the stock muffler is robbing me of HP. Considering I dont want it too much louder and definitely no loss of HP what do you suggest?

 

You'll get similar to OE sound but perhaps slightly louder and deeper with any performance muffler that isn't a straight-through design (Dynomax Ultra-flo, etc). Stick with Flowmaster Delta series, Dynomax Superturbo, etc. Any "turbo" design muffler will outperform the factory garbage can and be similar in sound.

If you are using a "T" after the muffler for dual rear pipes I'd suggest using a "Y" as a "T" will rob you of horsepower because the exhaust flow needs to change direction 90 degrees.

 

I'm sorry it is a "Y" after the muffler not a "T". If I opt with one of these how much am I looking at, and should I take out the "Y" and get one that has duel outs of the muffler? Or would that make it even louder? I guess what I am asking is what are the pros, and cons of having the duel outs of the muffler.