Example: car dragon - shows 6 pages of results in incognito, 3 pages logged in.

My blacklist is empty, so I don't understand why I'm getting less results while logged in.

Help?

the amount of posts per page is different

Perhaps being logged in has a different number of posts per page. There's a setting for that in the user account settings page. If you've changed it, that may be why, or it's possible user accounts have a different default than a logged out user.