I apologize for the stupid newb questons in advance... In general, I know how tunerswork and what they do. I know it's a flash device that reprograms your car's ECU to specific settings. I know it's supposed to boost performance. But that's pretty much all I know.I've never actually used one, or have seen anyone use one. So, in no particular order, here are some general questions I have:

How do they work exactly? Do they come from the manufacturere pre-set with specific tunes, or do you "tune" yourself? I get the impression that it's pre-set, but I'm not sure...

Can I do the programming myself, or do you have to go to a certified tech guy who does the tuning?

What are the pros of tuning? Obviously, I know you should get a performance boost, especially if you add on CAI and better exhaust system along with tuning, but can tuning be beneficial if that's all you do?

Does it void a new car warranty?

Again, sorry formylame newbie-ness. Thanks...