My fuel pump noise (both the old one and the new one I installed) turned out to be caused by a faulty pressure regulator up at the injector rail NOT by a bad pump. Parts counter man insisted that from my description of the problem I had a bad pump in the tank. He was wrong. Bad regulator was not letting excess pressure bleed off back into the fuel tank causing external pump have to work too hard. Thanks for the 2 suggestions, guys, they were both right. The electric pump delivers about 10 times as much gas to the injectors as they need. Excess is routed back to the tank. Could have been either a clogged return to tank line or faulty regulator. In my case it was the regulator.

Here's what I learned....

If the external electric fuel pump is noisy, pull the return line off the pressure regulator. Install a spare length of hose on the barb and run the other end into a can on the ground. Start the engine. Fuel should be rushing out of the hose leading into your can, even at idle. If this excess fuel that the injectors aren't using is NOT (mine was not) rushin out, there's a good chance your fuel pressure regulator (about $60) is stuck closed.

Volvo mech said he's put pressure gauges on cars w/ stuck regulators and the needle goes off the scale.