Hi alans1100,
your bike's ABS system is not transferable to the to the earlier models (95 and before) as they are quite different including the wiring. I have researched buying modulators and the ECU from overseas and have some sources.
They are still very expensive , not guaranteed to fix the problem, and I may need to buy additional later on.
I am interested in what others have done as I know this is an emerging problem for the ST1100.
My ABS was also reasonably troublefree until the last 12 months.
Regards
Garry