I have a 2004 Silverado 4wd automatic with a 6L 300 hp. What are some of the cheapest things I can to boost the horsepower

 

There are free mods you can do like descreen the MAF, and reroute the coolant line that goes though your throtle body(depending on how cold it gets where you live, it can ice) but the best bang for the buck is to have me reprogram your PCM, the site is not finished but check it out http://www.goodguysgarage.net

Now the site is down, you can call 316-258-0358

Jason
Good Guys Garage custom GM PCM proggraming

 

Read my - " SO YOU WANNA GO FAST POST," for some ideas.
GL
Greek