What Flowmaster muffler should I run on my 97 Mountaineer?

[bronchole]

What Flowmaster muffler should I run on my 97 Mountaineer?

I know that the Mountaineer (5.0l) that I am picking up at the end of August currently has a straight pipe out the back with no muffler. All 4 of the stock cats are there but no muffler. It also has a MAC intake kit. Other than that the engine is stock and has ~150K on the bottom end.

From what I am being told by my friend that picked it up, the sound is not that loud. Quite tolerable for everyday driving and long cruises.

I have 2 different models of Flowmaster mufflers in the “spares” pile. One is a 40 series, the other is a 50 series Delta flow. I can easily redo the ends to adapt to whatever pipe size is currently on the Mountaineer (I don’t know what size that is yet) so that is not an issue.

I live in California so smog testing is some level of concern. Power is always good to have and I don’t mind the idea of maximizing fuel millage. I realize that some of these desires are not necessarily compatible.

I am looking for some input on the 3 possibilities I have at hand:
1- Leave the exhaust as is (Cats in to a Y, thru a few bends and out to behind the tires)
2- Install the 40 series muffler
3- Install the 50 series Delta Flow muffler

Which will give the most efficiency?
Which will give the best emissions?
Which will give the best torque?
Which will give the best HP?

Thanks for your input.

 

[Essex4x4]

Which will give the most efficiency?
Which will give the best emissions?
Which will give the best torque?
Which will give the best HP?

Although I would go with the 40 series I cannot go with saying that a muffler really is not going to change horse power, torque, emissions or "efficiency." Unless you do a full header and cat back exhaust a muffler is just that... a muffler. It muffles sound not power. It might change your numbers a little bit but you won't notice it at all.

 

[FIND]

Go with whatever you think sounds best, because there will be almost no difference in any of those 4 criteria you posted. For future reference, nothing behind the catalytic converters will ever change your emissions. Horsepower, torque and fuel efficiency? Well, changes in those will not be large enough to be significant. You will never notice the changes without precise equipment to measure with.

My vote would be for the 50 series, because straight pipes suck balls and are loud, and the 50 series is going to be the most mellow... Though still a significant amount louder than factory.