2014 Nissan Pathfinder fuel problem

Recently had a tank of fuel go in the car full of dirt and water, it misfired badly and shuddered and ran rough, I had it sent by truck to a dealership. They drained the tank and "flushed" the line and cleaned the pump and filter. It has been sent back for the third time still misfiring badly under load, should I insist on new pump and filters and maybe injectors? Car only one year old, dealer said in anything happens in future to engine as a result of this it will not be covered under warranty! Fuel company has admitted fault and offered to pay!