couple things
1. CPO is def worth it, the n55 and N63 engines do have their stupid problems.
2. there is not alot of margin in used cars anymore because of the internet....especially with CPO. your expectation of them coming down $2000 is way off. your lucky to get the $500 off.
3. They cannot CPO the car if the tires are too low, so if it passed CPO, they arent going to just throw in new tires.... as the truck doesnt need it.
4. The computer tells them when the truck needs new brakes, they wont just change them under CPO. brakes are included in the maintenance of CPO.... so why not just get them when the car needs them