P0190 Code - 1998 Lincoln Cont

98 Lincoln Cont - 83K, ongoing P0190 code. Had Mech changed out FRP sensor. Service Light came on within a week. If I fill the tank up with gas, the check service light goes off in a day or two. When it gets to half a tank the service light comes back on. Also with about a quarter of tank, it has slight hesitation and a little rough idle. Going around corners or on exit ramp, more hesitation is noticable. With half of tank or more no problems. Not sure if its the regulator, it could be but I thought if that went bad you would typically smell gas inside the cabin...not sure. The dealer saying its the fuel pump, not convinced especially for $700. If it was the fuel pump the car wouldn't start correct?

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