My wife's Mustang had Borla ATAK's on it for 4 months before we installed BBK LT's with cats. The headers made a huge sound increase, but the sound type stayed nearly the same (still sounds like the ATAK, just louder).
Wife = 2012 Mustang V6 Premium Grabber Blue BBK CAI, BBK LT w/ HFC, Borla ATAK, MPT Tune, DSS Driveshaft, 3.73 FRPP Gears, BMR LCA's | Best = 13.5 @ 105
Husband = 2010 Camaro V6 Synergy Green Edition IPF Supercharger Best = 12.5 @ 111
Closest finish @ the line = Wife by 0.0028 seconds (4.79 inches)
Also own a 2014 Mustang GT Premium, Brembo Package, 401A, Comfort Package, Shaker Pro System, Pedestal Spoiler