As we all know by now, moving more air through the engine usually begins at either end. After uncorking the air-inlet system with the K&N filter, Rick's next step was to add a Bx Performance after-cat system. Talk about paying instant dividends. Meeting those federal noise limits must require a fairly restrictive factory muffler. The Bx systems added almost 10 hp and a whopping 15.3 lb-ft of torque at the peaks versus the K&N filter pull. Better yet, the after-cat allowed the 4.6 to make more power and torque throughout the powerband, justifying its $479 price tag.