Hey guys just purchased a 2013 GMC with the duramax. It has been deleted and I was told it has an EFI Live tune. It has a 5 position switch on the dash but no tuner unit attached. As I am new to these trucks, is there a way to determine what the tunes are? Purchased from a dealer that picked up truck at auction so no previous owner info. He told me that "normally" position 1 is stock, 2 is fuel economy, 3 towing, 4 & 5 are horsepower tunes. Is this "correct" or kinda correct? Should I feel differences when I switch the positions of the switch? Thanks for any info you can provide.