The only engines available in the Platinum in 2015 were the 5.0 and 3.5 EB. I'm sure the OP knows what he has, and this is not the first complaint I've seen here about a 2015 3.5 EB feeling sluggish. Something is not right, get it to the dealer. I wouldn't be surprised if something is wrong with the turbos and/or the programming.

 

This is what I was thinking. Cause I've driven both the 2.7 scab and 3.5 Eco screw both lariats and the 3.5 was a FX4 not certain any of their rear ends. But they both put me back in my seat and seem way more peppy than my 5.4 3v.
I'm thinking the factory tuning or turbos are messed up.

 

"First Ford, did I make a mistake?"....classic troll post on a Ford forum.
If you test drove the truck why did you buy it if the acceleration didn't suit you? Sorry but the troll alert went to Defcon 1.