Set this to 2x or 3x PSP. Going higher may cause stuttering on mid-range phones.
Extract the textures into PSP/TEXTURES/[Game ID] . If the "TEXTURES" folder doesn't exist, create it manually. Set this to 2x or 3x PSP
Open PPSSPP, go to Settings > Tools > Developer Tools , and ensure that "Replace textures" is checked. Optimization Tips for a Lag-Free Experience create it manually. Open PPSSPP