My understanding (which could be wrong) is that fuel rack sensor is an input to the EGR “computer”. Unhooking it shouldn’t change the operation of your pump. Perhaps it’ll make your car activate EGR at an in opportune time thus decreasing power. You can test this by plugging your EGR line and going for a drive.

Good luck.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 190k miles
97 C280 150k miles