Is your PCI modem a Win (software) modem? You can get info on TRYING to configure software modems here:
http://www.linmodems.org/
You will probably spend tons of time and go through heaps of frustration configuring these mediocre performers...
Or you can get a hardware modem, that will probably work the first time every time and give the kind of performance that you can count on.
Up to you...