For performance upgrades, there are several intake systems on the market and two major tune programs. Bad News Racing actually has a kit where you can get a Tune, a cable, and an Intake for $600. It is currently on sale for $550.
As far as warranty is concerned, any intake system will not void your warranty. Tunes may cause warranty "issues" with your dealer depending on what you select and how they are. Technically, nothing can void your warranty until something breaks and the modification can be proven as the direct cause.