Here are my findings so far:
The correct Bosch part number is 0580254036. This was confirmed with
Bosch Customer Support (800-283-1111). This was the number given to
me by MAAS Auto Parts (my respect for them is growing). They also had
the best price, although Linda at Carlsen Audi offered me an
895 906 091 A for $137, which is probably the same thing as Bosch #
above. But wait, it get more interesting.
Amidst all the queries, I called Audi Cust. Rel. and they actually
offered to render me some financial assistance (50%) with the repair,
since this is my second pump failure, and the new pump, 895 906 091 B,
is redesigned (not Bosch, according to dealer), significantly more
expensive, and is more durable. The catch is that the pump must be
proven as bad. Since I "resurrected" it, the damn thing won't quit,
and I suspect my wife might be driving a time bomb until it quits
again, if it quits at all.
When I mentioned that Marek Biela at Sudbury performed the first pump
replacement about 1.5 years ago, the chief mechanic had some bad
things to say (about Marek, who worked at Bernardi). This could be
politics, and close to gossip in validity, so I would take this with a
grain of salt. But I thought in all fairness I should post this info
to the list.