Electric fuel pump whistling

I have an injected 350ci and set up all the necessary additional fuel pump and reservior tank.Car has been running fine and now when you turn on the ignition and the pump starts its action a whistle starts and then stops when the pump stops.Start the engine and the whistle starts and continues while the car is running.Engine runs fine just this dam whistle sound.It runs 2 pumps.One push and one pull from memory.
I am ready to put it up on the hoist and pull the belly pans off(big job)
to check where the sound is exactly.
Any leads would help immensley.

 

Back to the top.Looks like my problem must have the HAMBERS stumped.
Plenty of looks but no answers.Someone suggested it may be like a water pipe where there is a vibration in the line?

 

possible cavitation? just a thought

 

The Holley "black" pump I have in my o/t car rattles up a storm even thought it's bolted in correctly with the rubber insolator in place... I deal with it.. I can't hear it once the engine starts...