the fuel consumption dramatically increased on my 89 Buick Riviera (runs welll, a little stronger than usual, but idle loops). Found fuel rail pressure to be 58 psi. replaced fuel pressure regulator twice now (aftermarket, not Delco AC) and pressure is still high, 59 psi. tested regulator with external vacuum source and niether of them dropped the fuel pressure when I applied up to 28 inches of mercury. is it possible both new regulators are defective? any suggestions welcome. thanks, Mike