I have a 2004 Chevy Suburban K1500 5.3L non flex and some mornings the battery is dead. Nothing is left on that would seem to drain the battery, ie. lights or plug ins. I have had the battery tested and the starter as well as having the alternator replaced when it did not need to be. Had it bench tested after being removed and it was fine. Still their is some kind of a drain on the electrical system that I can't figure out. Any suggestions or advice??