I've seen reference made that the serial number on this unit needs to be above #1044871 yet haven't seen an explanation why. What is the difference between units with #'s above and below 1044871?. I have an '03 QC 4.7 auto 4x4. Is there a performance difference or do features vary among the different engines that this model works with. I'm mainly concerned about issues regarding using one with a '03 4.7l

Thanks

 

Anyone know??