Hamburger Torque-Curve Technology Spacers: Available for Most Vehicles
Torque-Curve technology spacers from Hamburger's are said to not only seriously kick up the horses, torque, and mpg, but also pretty much eliminate the whistle that can sometimes be had with an EFI spacer. On a stock throttle body, a negative pressure zone is created on the upper, back side of the throttle blade when at partial throttle, which can create turbulence, slowing airflow and sucking valuable power. Torque-Curve EFI spacers were designed to zap out the negative pressure area. You're looking at about $100 for the spacer.
Hedman Hedders: 2004-2009 Ford F-150 5.4-liter
From Hedman Hedders are stainless steel headers for the 2004-2009 Ford F-150 5.4-liter. They feature a short-tube design (read: simple installation) and are manufactured from T304 stainless material. The mandrel-bent 1 1/2-inch-diameter tubes merge into a factory-style collector that'll bolt right up to the stock exhaust (and the catalytic converters are retained). The flanges are 3/8 inch thick to resist distortion. You'll find the headers priced from $500 to $600.
Hypertech Max Energy Power Programmer: Available for Gas and Diesel Apps
The Max Energy Power Programmer from Hypertech puts controlling engine efficiency, horsepower, torque, and fuel economy in your control. The handheld tuner is available for gas and diesel apps, as well as flex-fuel. For diesels, three stages of power are available, including one that maintains safe exhaust temps while towing. Max Energy also allows you to calibrate the speedo, raise or lower the top-speed limiter, increase shift firmness, and adjust the on/off temps of the electric cooling fan, among its many perks. Figure you'll spend under $400.