Improving your Chevy Silverado with air filters and chips (which modify the engine control unit (ECU)) is entirely possible and is a popular option given the ease of installation. You can switch out the air filter yourself, and you can knock out most ECU flashing with a simple plug in of a software module. The Silverado has a lot of room of improvement, given its truck-like EPA ratings of 15 to 22 MPG.
Find an air filter for your model year of Chevy Silverado that includes a thermal shield as well. A more efficient air filter can increase fuel efficiency all by itself, as it increases the air flow into the engine, allowing for more efficient combustion. However, the biggest increase will come from the thermal shield, which keeps the air coming in to cool the engine, making for a denser, more combustion-efficient air flow.
Install the air filter into the Silverado, making sure that the connection is snug. Just tighten the o-ring clamps till the air tunnel no longer rotates; it is also helpful to use thermal tape on the seams to both prevent air leaks and further prevent heating of the airflow.
Find a ECU flasher that supports MPG improvements; until recently manufacturers did not use ECU flashers to benefit fuel efficiency. Most of the ECU flashers just require a module in the diagnostic port on the Silverado, under the driver side console. Other flashers may require soldering, which is best done by a mechanic, as an errant piece of solder can break the ECU.
