93 deville burns alot of fuel, like a gallon a mile; no leaks in fuel line. Any suggestions?

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A ruptured diaphragm in the fuel pressure regulator will let extra gas enter the engine through the vacuum line to the regulator. Pull off the regulator vacuum line. Any evidence of gas? Let the engine idle a couple of minutes with the vacuum line off. If any gas starts coming out of the vacuum line nipple on the regulator, then that was the problem. Replace the fuel pressure regulator.
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