I've been wanting to install longtube headers on my 2007 sierra classic for awhile and now that I've noticed that the OEM exhaust manifold is cracked and one stud is broken I think it's the time to do so. Just wondering what info i should know before doing so. Do I need to have it tuned? I currently have a cold air intake, throttle body spacer and cat back exhaust but that's pretty much it.