I've been (and will probably continue to be for a week or so) distracted, but...

It sounds like your file doesn't match my file. You'll probably need to get the DRVRs from 7.1, like what I've got.

But... Are you sure the data pump is wired into the address space at all? The PowerBook Duo System devnote includes a pinout of the modem connector, and it is pretty modem specific. No address or data lines in the description.