what are some good external replacments to get more hp out of my 99 silverado 5.3?
so far i have a borla muffler, hypertec programer, tb spacer 4;10s, k&n intake
thanks

 

Lets try this over here

 

LOL try some free mods and weight reduction.
http://sshotrods.com/

As far as bolt on go, get some ls1 e-fans, ASP crank pulley, lt headers and a custom tune.
You should see a very noticeable with all this mentioned.

 

an 02 pcm with a good tune

 

take a look at people's sigs. and we will need to know a couple a things as well.
1. daily driver???
2. towing with her??
3. wanna be real fast and mod it heavily??
4. wanna mod conservativly and just be a good all around truck?

my first and foremost mod is a shift kit and a servo for tranny reliability. it is the weak link.then a custom tune after exhaust and intake. put in a cooler therm. then answer the above and we will be able to help out more. this can be a 1000.00 project and can climb to above 15000.00. the best of luck and let us know.