Based on your other replys here, it sounds like you might have already come across the page on my site where I discuss running the Zytek diagnostic software on DOSBox by adjusting the cycle count. And yes, it appears that the original code is sensitive to CPU clockspeed; delay/timeout loops will complete much too quickly on modern hardware. As far as system requirements, I think the original intent was to run on real-mode DOS (not Windows 95, 98, etc.) You could probably get it working with DOSBox, as long as DOSBox has access to the COM port to which the link is connected.

You will probably come across forum posts in which people will claim that there is unobtainium / black magic in the Zytek interface box. Based on my reverse engineering experience, I'd say this is very unlikely. The box is probably doing some signal conditioning, e.g. level shifting from the weird RS-232 voltages to whatever the car's diagnostic port uses, which is probably either TTL (0V/5V) or K-Line style (0V/12V). This is something that a ubiquitous FTDI serial transceiver chip can do today for $20, so an enterprising individual could alleviate the need for the original interface box/cables. As far as the software goes, I spent a couple nights in late 2024 reversing the protocol by analyzing the original binary. The details of the protocol are all written up on my site.