Dear überbox,

Good p.m. and may this find you well.

Here are the Volvo & Bosch part numbers, for Engine Control Modules (aka ECUs):

B6304F, 1991-early 1992.....35 47 841...0 261 200 528
B6304F, 1992 (EGR, EL)......35 31 061...0 261 200 507
B6304F, 1992-93 (EGR, EL)...68 42 498...0 261 200 996
B6304F, late 1992...........91 35 010...0 261 200 528

The Bosch numbers are those, which begin with 0 (Zero), followed by three, 3-digit groups.

Source: Volvo, pocket data booklet - Cars; 700,850,900, 1991-1996, p. 48.

You might be able to find one of these, at a salvage yard. You'll need to know the chassis numbers, which define "early" and late".

Hope this helps.

Yours faithfully,

spook