Always set is_new on node create rather than node_save().

plugins/FeedsNodeProcessor.inc

@@ -34,6 +34,7 @@ class FeedsNodeProcessor extends FeedsProcessor {
     $node->changed = REQUEST_TIME;
     $node->created = REQUEST_TIME;
     $node->language = LANGUAGE_NONE;
+    $node->is_new = TRUE;
     node_object_prepare($node);
     // Populate properties that are set by node_object_prepare().
     $node->log = 'Created by FeedsNodeProcessor';
@@ -112,10 +113,6 @@ class FeedsNodeProcessor extends FeedsProcessor {
    * Save a node.
    */
   public function entitySave($entity) {
-    // If nid is set and a node with that id doesn't exist, flag as new.
-    if (!empty($entity->nid) && !node_load($entity->nid)) {
-      $entity->is_new = TRUE;
-    }
     node_save($entity);
   }
 

plugins/FeedsProcessor.inc

@@ -137,8 +137,6 @@ abstract class FeedsProcessor extends FeedsPlugin {
    */
   public function process(FeedsSource $source, FeedsParserResult $parser_result) {
     $state = $source->state(FEEDS_PROCESS);
-    $entity_info = $this->entityInfo();
-    $id_key = $entity_info['entity keys']['id'];
 
     while ($item = $parser_result->shiftItem()) {
 
@@ -163,8 +161,6 @@ abstract class FeedsProcessor extends FeedsPlugin {
 
       try {
 
-        $replace_existing = $this->config['update_existing'] == FEEDS_REPLACE_EXISTING;
-
         // Load an existing entity.
         if ($entity_id) {
           $entity = $this->entityLoad($source, $entity_id);