Since there are so many Gnus versions out there this page does not contain diff style patches but instead the raw code. You need to find and replace the functions in your gnus with the functions listed below. Unless you use a recent Gnus that contain all patches, that is.
I have not tested this with every known Gnus version. To play it safe (wrt nnimap), upgrade your gnus to the latest development version.
Theese are patches not required for operation but adds variouse enhancements to Gnus. Patches here will hopefully be included in the experimental Gnus version sooner or later. As such theese patches are considered very experimental.