I don't think they can tell. But look at it this way, you will be modifying how the car came stock. My thought is easy. The preadator pulls your stock program, apllies changes to that program (WOT table and user selected things +/- fuel, etc) and re-uploads that image to the computer. If you want to make the computer "look stock" then you flash back the stock tune, unhook the battery overnight, and I will doubt they could tell.
In my case, I had the car tuned with the Predator, I know it is safe, but I'm still over the line. If it breaks, I pull out my checkbook.