Update - I only used the truck to tow my trailers and had only driven it without a trailer probably under 1,000 miles. So after I posted this message I decided to use it as my everyday driver for the past week. I found out that the truck does it without a trailer attached. I had to brake harder to get it to show like you would towing, but it showed itself. The truck pulled both left and right on about 30% of the stops. I'm taking it back to the dealer and having the service manager ride with me until it happens. I'm thinking it might have something to do with the brake proportional value. I get the feeling this is going to be one of those odd things for Ford to find.

 

The proportioning valve only affects the rear brakes, so I doubt that will be the problem.

slides or piston would be my guess.

 

Front brake calipers.

Take them off, clean them, grease the slides. If that doesn't fix it, replace the front calipers.