Pinch rollers and star wheels - do a search, it's a well covered topic.
I've had the pinch rollers replaced with the tan coloured ones. The tech said I had the latest star wheels (how can you tell if they are the new ones?).
How does this affect the printing in the sense that the paper has a lot of curl and the Z3100 does not have a vacuum hold down system? I'd really like to use GFS in my Z3100 as the sheets don't come in large enough sizes.