Here you can find the latest release of Systempatch i.e. 2.91 http://digilander.libero.it/ziosante/index_eng.html
SystemPatch is intended to be useful on AGA systems.
SystemPatch replaces some functions of the operating system with optimized ones, increasing the system efficiency in a multitasking environment.
I heard that it also speedup under WinUAE.