Even when it's not invoked in Startup-Sequence, my system will still waste at least 32 seconds, diddling itself (the HD LED literally blinks 32 times) before it loads WB with this PlexWriter hooked up. I've tried every possible termination combo on the 2091 and the drive itself. Even upgraded to 7.0 ROMS on the SCSI card, but no change. What I do to help speed things up is keep a CD in the drawer. As soon as it spins up and gets a read, the computer proceeds to boot, shaving lots of time off the "normal" boot process.
I don't have any experience with an 2091/PlexWriter combo, but maybe you should
move over to another SCSI controller and/or CD-player/writer if the system struggles
to recognize the PlexWriter..
I've succesfully mounted CD-writers to my A600/A1200 (PCMCIA CD1200 controller)
and A3000 (external SCSI CD-burner).