The jumping RPM's could be caused by your IAC (Idle Air Control). It's around your throttle body and you can take it off and spray carb cleaner in there if it's dirty and itll loosen up all the crap inside. People say it does and doesnt work, some people have had trouble with cleaning the IAC and say they ruined the IAC. If you'd rather buy a new IAC, I believe they cost around $75-100, if I remember correctly.

You can also try a product called Sea Foam. Dont know if you ever heard of it but it cleans the carbon build up. Im sure if you research Sea Foam you'll find plenty of reviews about it. You use it through your brake booster line and suck it up and let it sit for 15-30mins, then turn you truck on and it should smoke like crazy. But research it and you'll find more exact details on how to use it.

http://www.seafoamsales.com/motorTuneUpTechGas.htm

there's the offical site for the product.