Update imported feeds to only get one taxonomy term per node I have used feeds to import some nodes with taxonomy term reference. 

The source XML is the following one.

&lt;items&gt;
  &lt;item&gt;
    &lt;title&gt;Test 1&lt;/title&gt;
    &lt;body&gt;Test body 1&lt;/body&gt;
    &lt;term&gt;My_term_foo&lt;/term&gt;
    &lt;/item&gt;
&lt;/items&gt;


First import is OK. I edited &lt;term&gt;My_term_bar&lt;/term&gt;, and started importing a second feed.
After the second time, the node has both "My_term_foo" and "My_term_bar," but I need only "My_term_bar" from the second import.

Is there any hook_feeds_node_item_presave() I can use to alter the values being imported?

EDIT:

My final code of hook_nodeapi inpired by sel_space:

switch ($op) {
      case 'presave':
        if ($old_node = node_load($node-&gt;nid)) {
          $taxonomy = array_diff_assoc((array) $node-&gt;taxonomy, (array) $old_node-&gt;taxonomy);
          if (!empty($taxonomy)) {
            $node-&gt;taxonomy = $taxonomy;
          }
        }
        break;
    }
If data needs to be modified before it is saved use this module : Feeds tamper

For advanced modification use hook_nodeapi in drupal 6 with the insert parameter , with hook_nodeapi load the old node like this :

$old_node = node_load(node-&gt;nid);
$node-&gt;taxonomy = array_diff($old_node-&gt;taxonomy,$node-&gt;taxonomy)


So now you are sure that the $node contain only the new value , Hope this  will help