Disclaimer: The Context of "XISO"

This review will focus on the quality, playability, and technical performance of the classic Forza Motorsport games (specifically the original and Forza Motorsport 2/3/4) when played in this digital/ISO format, primarily through emulation or soft-modded consoles.

XISO

An is a modified ISO image file tailored specifically for the original Xbox hardware and file system. Why You Need XISOs

I notice you're asking about a "feature on 'forza motorsport xiso'."

4. Multiplayer / System Link not working in Xemu