Modern engines are engineered for maximum efficiency, so it's difficult to improve their performance substantially. However, there are some things you can do. Your 2014 GMC Sierra came with one of five different engines, and they can all benefit from the same upgrades.
A cold air intake is one of the least expensive upgrades you can add to your truck. They are designed around one principal: draw in more, cooler air and provide a smoother path into the engine. K&N Engineering makes a cold-air intake system that uses a high-flow oiled air filter and a smooth-tube intake and an air dam to hold out some of the hot engine compartment air, which they say produces about 10 extra horsepower. Advanced Flow Engineering makes an enclosed air intake system that they claim will help to gain 12 horsepower and 15 foot-pounds of torque.
Just as an air intake will help draw more air into the engine, a high-flow exhaust system will help expel those increased gases, thus increasing power. Advanced Flow Engineering makes a Cat-Back exhaust system which includes a larger pipe from the catalytic converter back, as well as a high-flow muffler. Corsa Exhaust Products makes a Cat-Back exhaust system that they say increases exhaust flow by more than 400 percent over the stock system.
Today's Sierra depends on its computer to make calculations to reach the best combination of driveability, power, fuel economy and emissions compliance. The computer is programmed from the factory to meet these needs. Aftermarket programmers are available to change these calculations, and you'll need one to maximize the effectiveness of intake and exhaust upgrades. Hypertech makes two programmers for your truck. You can opt for the Max Energy unit that can produce up to 13 horsepower or the E-Con programmer that can produce 11 horsepower and from two to six more mpg.
As well-engineered as today's engines are, it's not easy to improve on them, so you may be spending more money than it's worth for the small increases you'll get in power and efficiency. Some of the upgrades may also conflict with your state's emissions laws or void your manufacturer's warranty. Consider these things before you spend your money.
