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That code sets because the fuel rail pressure is low.
There is a common issue with these engines. It is the fuel pressure relief valve. This valve is a small plug in the end of the drivers side fuel rail. When they get hot, the start to open a bit too soon and set this code. There is a cheap solution to this. A shim that will hold the pressure back. Here is a website that sells these shims. http://dmaxstore.com/index.php?main_page=product_info&products_id=93
What is your mileage?
It will not be emissions, but it may be under the engine warrranty.
It could also be injectors, but if not warrranty, try this shim which MUCH cheaper than injectors at 400 each or more.