Ricoh MP C6501-background in non-image area

i have started working on a unit that has had many calls about copy quality.
after being cleaned for dropping toner on ITB ass'y the print/copy jobs have background even in non-image areas.
previous work was restarting all developers and replacing the ITB. Everything has been thoroughly cleaned and i have changed the black charge corona ass'y. Regular bond paper has a faint look of background however the glossy stock they use shows significant background even if single color is used the background seems to contain a color mixture. Print volume is around 65K and current engine version is loaded.

any ideas would be greatly appreciated by me and the customer!

sorry i posted in the wrong forum previously (newbie!!)