Hello,
Deactivating and deleting the plugin through the WP admin interface removes all the plugin files and options. Meta tags could not be generated by Add-Meta-Tags if it has been removed.
Do you use a caching plugin? If yes, please empty its cache, because your server might be serving cached content from the time Add-Meta-Tags was activated.
However, data that has been entered by the user (custom descriptions, keywords, etc), which is kept in custom fields, is not removed by default when the plugin is removed. But this data could not be possibly used without having activated the plugin.
I’ll provide more details about how this data can be removed at some other time (possibly tomorrow because currently I am on the road).
The bottom line is that if the plugin has been deactivated, the meta tags you see are _not_ generated by it.
What version of Add-Meta-Tags did you use?
Please provide more details or link to sample page or paste relevant HTML code here, so I can provide more help.
Kind Regards,
George