AFM's Danny Biggs crafted a special tune to make the most of the Velocity mass air and Power Pipe combination. To see what the Velocity and Power Pipe were worth on their own, Danny installed the parts with a tune containing the stock fuel and timing parameters. Then he moved up to the Performance tune for the remainder of the testing.
After opening the inlet, it was time for more boost. It's still hard to believe that factory supercharging has made power so easy to find. After pulling the stock blower pulley, the AFM crew installed one of Metco Motorsports' 2.6-inch pulleys (PN MSP2.60; $159.95) and accompanying idler pulley (PN MSI-90; $189.95). The pulley increases boost output, and the idler makes sure it stays increased by reducing belt slip. Adding the pulley resulted in 3 more psi for a total of 11 pounds of boost.
Since muffler swaps are so easy and common on the S197 platform, Rick elected to see what a Bassani after-axle muffler kit (BA-5407-5; $449) was worth on its own. The gains were modest, but the GT 500's personality greatly improved, thanks to more exhaust bark to go with all that bite.
The stock cast-iron manifolds are designed for leak-free, quiet performance in a compact form. The manifolds have to be compact because of the wide engine, so you're probably thinking it's going to be a challenge to get stepped long-tube headers in the same spot. Guess what-you're right.
The Bassani long-tubes are shipped as separate pipes to facilitate the installation on the car. Even with the separate pipes, the installation is time consuming and tedious. Reports of AFM tech Chad Kolakowski perched atop the engine tugging on pipes and speaking in the tongue of a sailor on leave were unconfirmed.
As you can see, the headers fit. As Rick said, they're hard to install because they work. In other words, they don't sacrifice performance (check the On the Dyno sidebar) for an easy installation.
Between the stepped long-tube and the Aft-Axle mufflers are a full 3-inch X-shape crossover with high-flow ceramic catalytic converters. Everything in the Bassani system uses slip-fit connectors and band clamps, similar to the factory parts. That makes for easier adjustment.