To convert a QIF file, just drop it onto QIF Categories. You can convert the input file in place or choose a different output filename. Every PCI modem I've ever seen has been a Winmodem. These things are like the old Apple GeoPort Telecom Adapters, in that they rely on the CPU to perform a great deal of the work that would ordinarily be done by the modem itself. Generally, this is a Bad Idea.
Modems are cheap and very good at what they do.
There's no compelling reason to tie up your computer's CPU doing something that a single chip can do much faster and better inside the modem. To get a Winmodem to work with a Mac, a guy would basically have to implement the equivalent of Apple's Telecom software. In all likelihood, the Winmodem manufacturers aren't going to reveal any technical details to this guy, so he's going to have to reverse-engineer the workings of each PCI modem he decides to support. Maybe he'll do an adequate job at this. Then he's going to have to test, debug, optimize, etc.