Any ideal why this printer prints dark at the top and gradually fades out toward the bottom of the page? Like on the config page the top part is fine but by the time it gets to the toner gauge the print is really faint. I have replaced the fuser and toner cartridge with a known working 8150 but nothing has helped. Any ideals would be appreciated. Also I adjusted the print quality from within the control panel--still no go. Thanks in advance