First, which engine do you have? Sometimes I can make guesses and be over 50% likely to be right, for example Sport probably has a 3.5L Ecoboost, but a '19 XLT, AFAIK, could have come with one of three different engines, the 2.3L Ecoboost, the 3.5L Naturally Aspirated, or the 3.5L Ecoboost.
I have no idea how much a warped exhaust manifold would cost to fix as I don't know if it can be fixed with the engine in the vehicle, nor am I even confident that this is what is wrong... just throwing ideas out there, about things to investigate to find the source.
I'm not entirely sure what "sounds like an airplane" means either, I mean I live near an airport and hear lots of different airplane noises. Is it like a prop propeller spinning, or like a jet turbine at speed, or like when a plane throttles back to land, or something else? If it only happens above a certain road speed rather than based on amount of throttle, then it might be other drivetrain noise rather than the engine itself (and not the exhaust manifold).
Possibly recording a video on your phone and putting it on a video sharing site like Vimeo or Youtube might help? Even if I don't recognize the noise, someone else might.
Is there any pattern to it? Does it only do it when the engine is warm? Can you replicate the sound with the vehicle parked, and revving the engine? If so then it might help to have a helper doing that, while you try to locate the vicinity of the noise with the hood up, or lying under the vehicle... staying away from hot exhaust pipes and catalytic converter to avoid burns.
As a new member to the forum, we have no idea of your means or diagnostic abilities to make it worth the bother to investigate yourself, rather than just taking it to a shop for diagnosis or the seller if under warranty. I mean it costs whatever it costs to fix and if you can back out of the deal if the seller won't make it right, that's what I'd do unless you bought it well under market value because the seller knew it had a problem, and then you might want to pay a 3rd party shop a diagnostic fee to find and to document what the problem is, then you have a better idea what your risk vs benefit is in keeping it.
Is Dryden in Canada? I don't know anything about Canadian vehicle purchase/warranty/defect/etc related laws, so someone in Canada can better advise about legal recourse if there is any.
