Google not indexing all pages

I am not sure that Google is properly indexing our site and I was hoping somebody could advise me on this.

We moved to Drupal a couple of months ago, importing 10's of thousands of articles from our old CMS into our Drupal dB. As part of the move, we built a mapping table and used mod_rewrite to translate our old content ids to the new Drupal nodes.

We used CCK to create a new article content type and created a module to display the articles in sections based on taxonomy.

We use path auto, so typically in our site, you will see www.domain.com/article/the-name-of-the-article at the atomic level.

Unfortunately, I have seen our site traffic drop away and so have been trying to identify causes.

Using Google's webmaster tools, I am seeing that Google has spotted our Sitemap and is seemingly indexing articles, but it is ranking almost all our pages low (and maybe that's just how things are).

The other thing though is, when I go to the Index stats, while it shows 64,000 results, most of them seem to be for top level pages, images, Forward pages or Print Node pages, as well as urls that show the redirect.

More to the point, when I search directly in Google for phrases that I know are in our articles, when it does return results, they will often be the section pages and not the node pages. If you click on the result’s link to these section pages, the teaser and link to the full story will generally be there. But, the bottom line is, the link the node doesn't seem to be showing up in the Google search.

We are in the process of installing the Node (key)words module in the hope that this is the answer. But, if anyone else can shed some light on this, it would be much appreciated.

Thanks,

Geoff