Sorry, I didn't see this post. Ignore my other reply.
Your driver (PCL or PS) will not affect scan quality as both of those refer to print languages and have nothing to do with scan rendering on the xerox.
Tiffm refers to multiple page tiffs. The Tiff format supports multiple page documents similar to pdf's.
If you are not getting the lines when scanning from the glass, then your strip of glass where the scanner rests during document feeder scans is dirty. You may not even be able to see the specks, but they are blocking the light from the scanner when scanning from the document feeder. Just keep cleaning it until the lines go away.
As far as scan quality, you may or may not have additional format options depending on your model. PLay around with all the settings available when scanning to see what works best. The only other option would be to photoshop the scans afterward. These scanners are built more for speed than quality so you probably will never get as good quality as you will with a flatbed scanner.
