You can also do the same thing with a CAI install. The stock air intake system has a large "muffler" (sound deadner) on the side of the air tube that connects the air cleaner filter box to the throttle body. If you remove this box, you'll get the same results, as this muffler deadens the sound. Even the 5.0's have a sound deadner on their stock intake tubes. Amaxed me why Ford put the sound deadner on the tube, then plumbed a "sound tube" to the firewall so the driver could hear the sound!
Three options: Get a 5.0 sound tube. Be sure to get all the parts. You'll also need a PVC 90 degree elbow to install onto your stock intake tube.
Get a CAI
Cut off the sound deadner box and fiberglass the hole it will leave, then paint the tube. This basically creates your own CAI, only with the stock air filter box instead of an open cone type filter.
If you want to install the sound tube from a 5.0 onto your V6, watch this youtube:
Mustang GT Induction Sound Tube Installation On My 2012 Mustang 3.7 V6 - YouTube