Small Engines (Lawn Mowers, etc.): Craftsman muffler # 137352, straight pipe, pipe design

Question
I saw that this muffler is now being made with a straight pipe instead of a "S" shaped one that's on my mower. What would the benefits be, if I replaced my current "S" shaped muffler with this new straight pipe design? How much more horsepower does this new design give?

Answer
First of all, we need to get a few things straight. Any bends in an exhaust pipe are the points that get very hot, so by adding a straight pipe, you would reduce heat. I cannot tell you very much about the backpressure that this new muffler offers because I do not know what the internals are shaped like. Another benefit may be sound reduction. It is much easier to put a muffler on a straight pipe then on an S-Bend. And finally, based on the backpressure ratings, you could possibly increase horsepower...but more likely, torque. Tourque is the turning force that an engine produces. The more torque, the more turning power. Therefore, torque is really the true measure of an engine's power. If you need to replace the muffler, then the straight pipe would be a good idea; but if not, then the gains that you would get from the straight pipe probably aren't signifigant enough to go out and buy one just because you think it is better.
-Steve