If the car has a tune on it you should have gotten a handheld tuner, like a SCT or Diablo Sport with the car when you bought it.
yeah you "should" but unfortunately that is often not the case, I was one of those cases where the car had been tuned but the dealer did not give me the tuner, in fact the dealer swore up and down that it had not been tuned
A Ford dealer can read the program in the ECU and can tell if it has been reprogrammed (aka "tuned"). I had to do this with mine. They cannot tell you what has been done in the tune, only that it has been re-flashed.
If possible, the best bet is to get in touch with the previous owner and ask them. Unfortunately many dealers will not do that for you, due to "privacy" bull crap.