Poor print quality
if cartridge and drum did not solved this problem, this meant that problem lies with mirror or tracking system and repair that bits is usually beyond home user.
firstly try to check and clean all rollers and traction system, work from tray catcher up, follow paper trail and check for stuck hair, bit of paper or any other debries, clean all rollers. then follow paper procedure below:
as this is easy, create a page of white and black about 10mm lines and then print full page on 120g watercolour paper (this is bit grainy paper which will work as "scrub" of the system), this will remove if any, debris from transfer drum in most cases.
if these solution do not work, if you game, remove back, mark all wires where they go, then remove motherboard panel, mark mirror position, clean it up and this will solve the greyness problem, or kill the printer totally...