ok, finally got around to fumble fingers on the fone, and this is what they
said:

dealer (jim ellis, atlanta, 800-653-5547)
1983-1985 water cooled:  part # 025-906-265  <no suffix>
                         ONE-WIRE  $39.60

1986-1991 water cooled:  part # 025-906-265 B
                         THREE-WIRE $133.25  <!!!!!>

from the FLAPS:
bosch parts ...
1983-1985 water cooled:  part # (old) 0 258 001 929
                         part # (new) 11-929 (apparently bosch is screwing
                                              around with their system)
                         price? he didn't have one cause they don't stock
                         these any more.
1986-1991 water cooled:  part # (old) 0 258 003 931   <odd. those last three
                         part # (new) 13-931           being 931 instead of
                         price: $100.00                031, like on mine>

for generic 'replacement' brand:
83-85  $34.85   <and you have to splice the wire for connection>
86-91  $63.31   <and you have to splice the wires for connection>

he (FLAPS guy) claims they don't have any problems with the generic brand,
so ...

but if the dealer (ellis) is dumb enough to sell the 83-85 one for $40 and
the FLAPS wants $35, i think i'd call ellis. :)  funny that he went up so
much on my 88 sensor. :(

hope it helps.
joel