Is that a fairly easy fix?

yes, when I turn the truck off the gauge needle goes back to zero boost. as soon as I start my truck needle pegs to max boost on guage and stays there regardless of how I drive or my speed.

I have an 08 6.4 with about 120,000 miles. Today the ford stock turbo boost gauge in the dash stuck on full boost. Truck seems to be running fine.Why would gauge be stuck on full boost like this?