BLACK LINE I have a black line running across each page I print.

The drum With poles can cause this fault (a black line followed of one white) in that model of machine, replaces cylinder blade and develop and adjust TD and ID sensor.

Greetings,
usually this would be either a cartridge or a fuser.since you changed a cartridge and it's still there.most likely it is the fuser.

you could double check by doing a half stop test.start a print from tray 1 and when the trailing edge of paper is just entering the machine,open the printer to stop print and take out the cartridge,open it's shutter and look at it's drum and the paper just underneath.if the issue ios not at either of those places,then probably the fuser.

if you take out the fuser ,you may be able to see an issue with a fuser roller.like a tear or other anamoly.
Also More than likely your fuser is peeling. Pretty easy to check...power down printer and pull rear door then unlatch the fuser and look at the fuser rollers...more than likely the bottom roller is peeling on one side...you'll know it when you see it...

Regards,
TechSup1