Two bad new fuel pumps?

[nde264 at lulu.it.northwestern.edu]

Six months ago I had the fuel pump and filter replaced on my 89 90q (211k
miles) as preventative maintenance.  I noticed about a 500 Hz tone coming from
the fuel pump shortly thereafter that sounded much louder inside the car than
outside, but still audible under the car as well.  I took the car back to the
mechanic that I had replace the pump and he told me to get a new pump in
immediately, that this one should not sound like that.  He also suggested that
I replace the rusty accumulator and fuel lines between said pieces.  I had
ordered the pump from blau and had another pierburg pump shipped.  I also
bought the new lines and accumulator and took the parts to my mechanic.  He
replaced these, and the pump was silent at the time of replacement, so I was
happy.  Now, the new pump has also developed the same 500 Hz tone.

At first, I suspected that there might be something wrong, clogged, etc in the
fuel system, but the original bosch pump that I had before only had an aubible
buzz, and worked fine.  Then I noticed that with multiple electricals on
(defroster, heated seats, headlights, fan, etc.) the pump's tone dropped in
frequency at idle and came up to the same 500 Hz with engine speed, but at idle
with no auxiliaries on, the pump is getting over 12V.

With the original new pump, I was autocrossing and getting out of first gear,
the engine stalled, I feel that the system probably vapor locked.  I had also
had the car lose power at full throttle and lurch around 5500 rpm once before.

With the newer pump, I have noticed that the cold start valve begins
pulsing/clicking when I give the engine any gas, presumably to richen the
mixture (oxs replaced 2000 miles ago).

Any btdt with fuel pumps going bad within months of replacement, twice?
Clogged injectors, not enough power going to the pump, etc?  Do I just take the
car to blau, and have them troubleshoot why their pumps are failing in my car
(I'm two hours from them)?  Get a bosch pump?

TIA,

Nathan Engelbert
89 90q (insert annoying tone)