They are a very well marketed product...and also very high priced to just get a "sound" that you want. Certain engines make certain sounds...I4...V6...V8...I6...and flat 4's and flat 6's (Subarus).
Aero and Borla are great products but you pay for the name
2006 Jeep Liberty CRD...Founder of L.O.S.T.
OME 2.25" Lift w/ Toyo Open Country HTs 235/75/16s
ASFIR Alum Eng/Tranny/Transfercase/Fuel Skids
2002 Air Box Mod...Air Tabs (5) on Roof...(3)each behind rear windows
Partial Grill Block with Custom Air Scoop and 3" Open Catback Exhaust
Lambretta UNO150cc 4 Stroke Scooter
engine basics 101. better flowing exhaust=power+economy. at the same time, bigger isn't always better because fluid dynamics shows that as you increase diameter of a pipe, speed goes down. decrease pipe size speed goes up. key is finding the balancing point where you have a small enough exhaust to keep the velocity up and get gasses out but not so small as to be a restriction.
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
mechanic, carpenter, stagehand, rigger, and know-it-all smartass
"You don't get to judge me for how I fix what you break"
i think there's an article somewhere on autospeed.com, were they replace the stock exhaust with one for a bigger engine... they do take what's mentioned above into account i believe, so it's not simply the bigger the better, but the bottom line is that you might be able to get better FE or performance and perhaps even better sound by replacing the exhoust with a stock item form another vehicle that has better flow.
I put a 4 inch diameter exhaust on my truck and got absolutely zero fuel economy improvement.
2000 Ford F-350 Super Cab Pickup
4x2, 6 speed manual
Regeared to 3.08:1
4 inch suspension slam
Aero mods: "Fastback" fairing and rugged air dam and side skirts
Stock MPG: 19
Summer MPG: 27.0
Winter MPG: 24
Yeah I totally agree that improving exhaust flow should improve FE, but Aero specifically claims an increase in MPG. In fact, they have a 1997 Eclipse Turbo as going from 18 mpg before the exhaust to 22 mpg afterwards. I find that a little hard to believe but the muffler technology they use does look very unique. Nobody here has ever installed an Aero Exhaust I guess?