Tunes aren't ecu swap like back in the day...these days you just plug into the obd2 port and reflash the factory ecu with different programming. How detectable things like that are depend on what you're going in for. If it's a general oil change, probably not a big deal. If you're going in b/c your turbo is toast, prob best to take it off. There is a lot of debate whether they can or can't detect them, but my bet would be they could if they dug deep enough in the coding and data stored, however that requires a lot of work and your average dealership isn't equipped to discover that.