I just got the flowmaster 40 too. It's got a nice rumble at start up and idle.. and during acceleration. I can barely hear it cruising down the road, my engine makes more noise honestly. But, I didn't want to be able to hear it drone anyway on long highway trips.

I don't know how much "break-in" time a muffler needs, but I've heard they get louder? I could be wrong. The super 44 is supposed to be louder. I will eventually dynomat the interior anyway, then I might try for something louder. But, my exhaust guy told me I could bring it back in a week if I didn't like it and try a different muffler, but so far I'm happy.

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2004 Ranger Edge 4x4, 4.0L SOHC, 4.10's, Black, Step-Side Bed, Quad Cab, 3" PA Body Lift, Underdrive Pulleys, Flowmaster 40 Catback, Mustang GT Disc Brakes
33x12.5 Goodyear Duratracs, 15x8 MB Motoring Overdrives, STX/Sport Grille, Explorer OHC & Auto-Dimming Mirror, Blacked Out Headlights & Corners,
Smoked Altezza Tail Lights, 35w 4500k Hi/Low HID Heads & Fogs, Hella 500ff's, Ultra-Gauge, Red LED Interior