my experience with a domestic producer (GM) tells me that if you flash your computer, it IS detectable, no matter what the tuner may tell you. GM is now voiding power train warranties if they detect that you have "tuned" your vehicle. And there have been instances where the folks reflashed back to a GM tune and THAT was detected, and the warranty voided. Granted there is still a lot of debate about what you should or should not be able to do but why take that chance??
Now, if Dinan or one of the other tuners will back up the warranty, then you might be okay. Bottom line, if you are going to do a reprogram, do LOT'S of homework.

Good luck.