The "kit" seems to be simply consisting of a 8K SRAM chip, to be used as replacement for the printers built-in 2K SRAM, increasing the buffer size by 6K.
The kit doesn't seem to be required for newer DMP printers - according to [[Media:LQ3500di and LQ5000di Leaflet (English).pdf|LQ3500di and LQ5000di Leaflet (English)]] and [[Media:AMSTPRINT Leaflet (Norwegian).pdf|DMP3160/DMP3250di/DMP4000/LQ3500/LQ3500di/LQ5000di AMSTPRINT Leaflet (Norwegian)]] - these do already have 8K Buffer RAM built-in.