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I have attached a basic vacuum schematic for you to review. The first picture shows five components. Number five is the regulator. Picture two is a list of the components by number. Take a look and you will see that vacuum to the fuel pressure regulator comes direct from the throttle body. Either there is something plugging the hose, or there could be a carbon build up in the throttle body preventing vacuum from getting to the regulator.
That is the first thing I would check. Do this and let me know what you find.
Images (Click to enlarge)
Tuesday, July 10th, 2018 AT 8:06 PM