Mods will void a warranty if they aren't reversible... Remember, the dealer is allowed to void your warranty if they want to. Do not believe the hype about the laws. A law isn't a law unless you hire a lawyer and file a lawsuit to enforce it. So if you're really worried about warranty then only do mods that are reversible.

For myself, I've done the Code3 pulley and needswings intake. These are very fast installs and very fast reversals, and provide quite a different driving experience. It changes the whole car.

Also, a sprintbooster is good too. It changes the throttle signals and will help a mild/sissy driver (like me) electronically turn into a much more aggressive driver.

I didnt pick simple mods to protect warranty though, I'm almost out of warranty anyways, I just picked them because they're effective, fast and I'm not interested in constantly working on the srt-6 like I've done with past cars.