There’s not much power to be gained, if any, from axle back upgrades at this point in the car’s engine modification cycle because the stock exhaust is pretty decent to begin with. The Roush exhaust is definitely louder now, but not obnoxious.
It has a deep low rumble at idle and sounds “buff” at WOT as the engines RPM climb. With more mods in the future, the lower backpressure of the straight through Roush mufflers might start to contribute towards power gains.
Next, Whiteline did a mild brake upgrade on the Mustang. With a 4 piston caliper and a 14″ rotor on the stock front brakes, the Mustang was pretty well equipped from the factory. To keep things simple for consistency when testing new suspension components, Whiteline wanted to keep things pretty close to factory original so the cars original brake bias and stability control would not be affected while the suspension was getting changed around. For this reason, the stock brake pads were retained for now.