Emission controls require the use of the stock air box with its hydrocarbon trap element, and that’s the way Vortech sells its Mustang GT blower kits. For off-road applications such as our track testing Vortech retails this optional Competition Air Inlet at $290.95. Vortech says its CAI requires custom tuning because it flows more air, and is worth 0.6 to 1 pound of boost over the stock intake on a stock engine, or about 25 hp. Gains increase the higher the state of the engine tune, so while we didn’t test the stock airbox with the Boss intake, the CAI is clearly worth even more at the Boss’ higher rpm. Vortech notes its CAI offers a bellmouthed entry and seals to the stock through-the-grille snorkel and bottom of the airbox to reduce hot air intrusion.