Connect the USB drive or external hard drive used with your PS2 to your PC.
The PS2 uses USB 1.1 ports, which are inherently slow. If edits do not fix performance, use a PC defragmentation tool specifically on your USB drive. Fragmented ul.cfg chunks force the PS2 laser emulation to stutter. To help tailor future troubleshooting steps, let me know: ulcfg ps2 editor