I want my plugin to change tag keywords

I currently wrote a aimplw plugin that does a str_replace of the placeholder %sbName%. I use add_filter for ‘the_title’ and ‘the _content’ to successfully replace any instance of %sbName% in my posts or a post title text that I am using for a specific blog.

I would like to also include this placeholder variable in tags so that they are dynamically replaced when both tags are displayed and when the keyword metatags are written in my page header. I have been using either headspace or SEO ALL IN ONE to write my headers.

Is there an add_filter option or some other way to have my plugin act on the metatags and normal page tags (the_tag) before they get written?

Ideally, I would also like the meta description to also read these changed tags.