Hi there! It's pretty easy to get a couple of extra horse powers with simple bolt on performance parts like a cold air intake and performance exhausts. They will eliminate restrictions on the way of the airflow and improve the overall speed of the exhaust gases. On top of the performance you will also get a pleasant sporty exhaust tone. Except for the Intake and exhaust you can also use a performance programmer. It's a simple tuner that will help you to adjust the engine and performance parameters to squeeze a couple of extra horse powers from your engine.
You can view the list of all performance parts available for your 1999 Silverado on this page: https://www.carid.com/1999-chevy-ck-...ormance-parts/

If you're into some serious performance improvement, there is a bolt on supercharger available for the 1999 Chevy Trucks with 5.7L and 7.4L engines: https://www.carid.com/1999-chevy-ck-...120684012.html