To acccompany the Flowmaster after-cat, and to provide that trademark Mustang sound, we chose BBK Performance’s X-shape crossover pipe (PN 1669; $219.99). BBK calls this its ’99-’04 Mustang 4.6-liter full-length X-shape crossover pipe. It is a direct replacement designed to bolt up to the stock exhaust manifolds at the front, and a stock-style after-cat. The 21⁄2-inch BBK X features CNC-mandrel-bent aluminized tubing with BBK’s unique die-stamped performance Xtractor center X-section for maximum flow and horsepower. We chose the X-shape crossover pipe simply for the sound it would provide our Bullitt.