Newbie with a question about tuners

Hello all I am leo and new to the site. Lots of great info around here. My question is about warranty. I have a new (06) F250 and after reading in the owners manual about black boxes recording any mods that are done. Is this true. I cannot take the chance of voiding this warranty. I have heard lots of good things about tuners and some bad. I am leaning heavily toward the SCT. I have a good freind that has alot of custom tunes that work well. I don't really want to do anything more than a tuner. Anyone with any thoughts on this? Can I get away with a tuner without voiding the warranty. Thanks in advance.