what are some things i can do to my 1999 chevy silverado 4.8 to give it more hp?
basic things that will help are a more free-flowing exhaust and a cold-air intake. you could also get a computer programmer. you will see more gains from intake and exhaust. to get the most from the programmer, you will have to run premium fuel all the time.
It all depends on how much you want to spend. You can either = #1 - Open up the exhaust to 2 or 2.5 inch after the catalytic converter so the engine exhaust breathes easier. #2 - Go to an open air filter type element (cone shaped) so that the intake can "flow" air easier inbound. #3 - Add a turbo/supercharger/blower unit. #4 - Change the cam. #5 - Change the injector sizes and reprogram the ECU. #6 - Change the crank shaft to a "stroker" crank. #7 - Change the heads and install flat top pistons creating higher cylinder pressures. #8 - Change out the 4.8 for a 5.7 if all else doesn't work. Figure out what you "really" want from the truck before spending any money. Look on my CarGurus home page behind the picture of my Ford Ranger (click on it) and you can see the cars I have built over the years in case you want to know where I'm coming from and what kind of knowledge I have.