Over the years, vehicle manufacturers have borrowed some of the power-making secrets of the aftermarket to improve their products. A good case in point is the newest line of GM trucks. Equipped with either the 4.8 or 5.3L V-8 powerplants, these trucks make great horsepower and torque right off the showroom floor.

One of GM’s borrowed power secrets on the new LS-1–based motors is the use of a high-flow exhaust system with header-style cast-iron exhaust manifolds feeding into a 3-inch exhaust system. While the new setup is good, there’s always room for improvement. Enter Flowtech Performance’s new Fantom after-cat exhaust system from the folks whose name is synonymous with performance: Holley.

Flowtech has designed an all-new line of after-cat exhaust systems for later-model trucks and SUVs that takes the design elements used by the factory to the next level. Built from mandrel-bent, 16-gauge aluminized tubing, the Fantom exhaust system improves exhaust flow approximately 20 percent for increases in horsepower and torque, while also adding a powerful sound to your truck. The system exits in the stock location and uses all the stock hangers for an ultra-easy installation. The finishing touch is a T304 aircraft stainless steel tip.

Installation is a simple R&R affair. We followed a Fantom system installation on a 2001 GMC shortbed pickup at Ace Muffler in Santa Ana, California. We also ran some before-and-after dyno numbers on the truck to verify the performance gains. The hardest part of the install was removing the stock exhaust system, which had to be cut in two pieces to get it out from under the truck.

If you’re in the market for a simple after-cat exhaust that sounds good, makes power, and can be installed in your driveway, look into Flowtech’s new line of Fantom systems.