I think it's related to constructive interference at different engine speeds, so switches w/ access to different exhaust lengths would be the best. Kinda like ACIS... But, for any new car it's easier to just optimize via exhaust valve openings. Maybe it's easier to drop one of those new fangled engines in than screw around w/ some funky system?

Yep. Keeping it on the exhaust is an issue. Thats why the tip that JCWhitney sold was supposed to be welded on. It also had a spring loaded butterfly that opened up for WOT.

I just like to hear the motor. I am kinda old school. Don't like automatics either.

Which V-6 in what vehicle, and you wouldn't by chance have a recording of it, would you?

That Accord goes fast enough to get a speeding ticket? :p ;)

A car requires back pressure to make torque. The smaller the engine, the more back pressure is required. For the OP I would leave the stock exhaust alone, unless it needs to be replaced. You will burn more gas trying to get the mass of the car going if you lose torque on the bottom end because of a 'bigger' or more free flowing exhaust.

First off, most people never see an increase in mpg when the car has more power, resisting that urge is one tough challenge, perhaps more so if you haven't driven 10-20 years with an impeccable driving record. :p

Most people, once the power is there, git it.
Hence they end up getting less mpg and they wonder what it was all about?

Theoretically speaking, increasing SPARK or AIR would yield better mpg IF you can keep your foot off the throttle, but a self-admited ricer? It takes a lot of self-discipline, kind of like those old grey-haired guys you always see driving the super fast cars doing the speed limit, about like that. Oh yes, age helps.


Now to install a muffler...
With a high flow exhaust system you need more than a muffler, you need pipes and a high performance manifold, in addition to a second cat, what you really need is called 'dual exhaust with headers,' and this is impractical because the cost of this runs 4-6-700 DIY and you're easily looking at a few thousand with a mechanic doing things, and of course muffler work usually requires welding.
And no, a muffler alone won't do squat.

For all that and the purpose of experimenting you're as well off installing Double platinum spark plugs, some decent high performance spark plug wires (such as Accel's 8mm or better yet Taylor 10.2mm), and a high performance cap and rotor.
DIY will set you back 1-200 and now that you're getting serious SPARK you can see for yourself if the +power = +mpg line of thinking is right for you.

But no, in most cases it will not increase mpg, but as much if not more so because once folks feel the power there's not much doing.

The trick is to resist the urge and actually use less fuel than before the upgrade, give it less throttle to accomplish the same acceleration means the increase in SPARK (and/or AIR) does the work while less fuel is used in the end.

The decrease in torque has less effect than the increase in HP, in the battle of horsepower vs. torque it is the horses that always win. Yes, you can manipulate torque and horses to a point and even to the extreme, but no matter how well manipulated a torqued setup gets, it's the vehicle with the most horsepower that wins.

Although impossible in a real life application (because horses and torque can't have one without the other), in the following case example:
A car with 100 horsepower and 0 pounds of torque
vs.
A car with 100 pounds of torque and 0 horses.

The car with 100 horses would win, every single time.
Yes, if it were possible, and we agree, leave the muffler alone :p