LIGHT UNIFORM STREAKS ACCROSS PRINT

Question

i have a Canon Pixma pro 9000 which is exibiting parralel streaks accross the print. they are the right colour but lighter. I have deep cleaned the head and aligned the print head but to no avail. the lines are about 2 mm apart and are the same no matter the size of print.From what I can see all cartridges are working corrctly. Is there any thing I can do??kind regards.... bernard