If you keep your stock H-pipe on and install an aftermarket muffler, the sounds will not be too loud. Flowmaster has a throaty, aggressive tone to it. Flows are loud at idle and super loud at Wide Open Throttle. While the Borla's offer a deep tone, that is quiet at idle, and really makes noise at WOT. If you don't want your exhause to be too loud, then I suggest Borla's (if you have the $$$) or MAC mufflers.
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'94 Cobra
308ci, ported GT-40 heads, Crane 2031 cam .513"/.529" lift 276°/282° duration, 70mm TB, Custom 80mm MAF, JMS chip, Vortech S-trim 8#, MSD, TREX fuel pump, Accel coil, 3.55's, FMS 1 5/8 headers, BBK Offroad H-pipe, and 2-chamber flows.
1994 Mustang Cobra
Check out the pics of my Motor Buildup!