I just installed the 87 octane tune on my truck this evening. And i must say i am very pleased with the power and trans changes. BUT!!! The book tells users that "if" you have onstar you need to remove the fuse for the radio before you install the tune. Well i got news for those guys. I drive a base model 4wd with no options and the tuner crashed 2 times before i pulled that fuse out. As soon as i did BAM. Backed up the original tune and installed the new on with no flaws. So my word of advice is if you are getting ready to put a Diablo tune in your truck save yourself the headache and just take the dang fuse out.