2000 GMC Sierra with 5.3 how to get more power?

I have a lifted 2000 sierra with a 5.3 and im looking for more power. I already have a cold air intake, magnaflow exhaust and im ordering long tube headers soon. I want to put a cam in it but dont know what cam i should go with and I heard I could put a trailblazer ss intake manifold on to help out? Any thoughts?  

im dealing with the same situation, and i've been talking to my local custom shop that loves dealing with these engines. I was told the intake manifold can be changed but theres absolutely no reason to change the current one out(i know it looks bad but apparently you can lose torque with a new manifold and only a slight increase in power, sometimes decrease). Longtube headers are the way to go but to really pull it all out, you'll wanna swap out your torque converter for a trailblazer 4.2ltr one, it'll raise your stall and youll in turn feel like you've gained power. If you wanna go big, go with an 02-04 Z06 cam for your engine, you'll lose the low end torque but youll find it higher in your revs while pushing out about 30-45 more hp. Having that with all your current bolt ons will take your power somewhere around 385 or more. Hope this helps and if you decide to do it, please let me know how it is, i been researching this for about 2 years now and im about to install everything around next may when i get back to the states so i'd love to know what my 01 Z71 will be able to ***

good luck  

by the way, would anyone happen to know if the 2001 z71 auto tranny for the 5.3 will fit the 6.0 for that year?