Review on Flowmaster 843041 Delta Muffler 409S by Josh Elkins

I use one of these on my wife's 2004 Mercury Grand Marquis (2 Valve 4.6L V8). I removed the secondary catalytic converters (the primary catalytic converters are still there and still emitting emissions, so take it easy) and built a 2.25" Y-pipe that transitions into a single 3" pipe , which comes out at the back of the bearing (although and with a much larger pipe). I have regular 40 series mufflers on two other cars (a double 2.5", a double 3") and the Delta Flow technology reduces the internal resonance compared to these. The tone is slightly different but still clearly Flowmaster. With factory gearing, this muffler won't irritate at cruising speeds between 45 and 80 mph, even with overdrive turned off. But even in a reasonably well insulated car like the Marquis you definitely notice it, I probably wouldn't get louder (i.e. normal 40 or Super 44) with an insulated everyday driver and that might be borderline in an older car with less sound absorption.