HYPERTECH IS CRAP, Crap, Crap x10000000 on gas chevy trucks, i know i wasted money on 2 of them. go with a custom tune. blackbear performance. since its an 08 you might want to spend the extra money and keep your original computer for warrenty work. just check his website. just remember that on your 08 you have a pcm to control the engine and a tcm to control the trans.
im getting one of his scan cable tunes in the next couple of weeks. justin has great customer service so far, answers all my stupid questions.