That is condensation in the exhaust and is a normal part of the combustion process.
So it's tuned and you can't return it to stock? That sounds like your problem. Call @GooseTuned and see if he can help you reset the PCM. You will need to buy a tuner but talk with Goose. If he can't help you might need to buy a new PCM and have Ford install it.
The dealer cannot diagnose an issue caused by an aftermarket tune. The tune won’t set codes because it literally alters the parameters under which a DTC will set. Not sure why you keep bringing it back to them hoping for a different result, you’re wasting their time and yours.