Fuel Pump Pulsator ?
 

I think that is what its called, Its on the fuel pump pick-up on the return line in the tank. Brownish in color rubber piece kind of flat.

What does it do?

Do you need it?

While putting in my 255 I remembered when I put in the 190 that it had a tear in it. Been driving the car like that for two summers.

What problems with out it?