How to debug queries and exports sent to Salesforce?
If you're using Ubercart / Salesforce Integration, you can use the following patch:

Drupal 6

--- a/uc_salesforce/uc_sf_order/uc_sf_order.module
+++ b/uc_salesforce/uc_sf_order/uc_sf_order.module
@@ -635,6 +635,7 @@ function uc_sf_order_export($order, $name, $sfid = NULL, $manual = FALSE) {
     // Export the object to Salesforce.
     try {
       $response = $sf-&gt;client-&gt;create(array($object), $map-&gt;salesforce);
+      drupal_alter('uc_sf_order', $response, $sf);
     }
     catch (Exception $e) {
       drupal_set_message(t('Error exporting order to Salesforce.'), 'error');
@@ -681,6 +682,7 @@ function uc_sf_order_export($order, $name, $sfid = NULL, $manual = FALSE) {
         }
         try {
           $product_responses = $sf-&gt;client-&gt;create($product_objects, $uc_order_products_fieldmap-&gt;salesforce);
+          drupal_alter('uc_sf_order', $product_responses, $sf);
         }
         catch (Exception $e) {
           sf_dpm($e-&gt;faultstring, 'Ubercart order line item exception');
@@ -718,6 +720,7 @@ function uc_sf_order_export($order, $name, $sfid = NULL, $manual = FALSE) {
       else {
         $user_object_export = salesforce_api_fieldmap_export_create($user_map_id, $account);
         $user_response = $sf-&gt;client-&gt;create(array($user_object_export), $user_map-&gt;salesforce);
+        drupal_alter('uc_sf_order', $user_response, $sf);
         $account_sfid = $user_response-&gt;id;
       }
     }


and then you can define the following function:

&lt;?php
/**
 * Define debug constant
 * To activate, run: drush -y vset foo_debug 1
 */
define('FOO_DEBUG', variable_get('foo_debug', FALSE));

/**
 * Implements hook_TYPE_alter().
 */
function foo_uc_sf_order_alter($response, $sf) {
  $xml_request = $sf-&gt;client-&gt;getLastRequest();
  $xml_response = $sf-&gt;client-&gt;getLastResponse();
  FOO_DEBUG ? watchdog('foo', "UC Salesforce XML request/response:\n&lt;br&gt;Request:\n@req\n&lt;br&gt;Response:\n@res", array('@req' =&gt; $xml_request, '@res' =&gt; $xml_response), WATCHDOG_NOTICE) : NULL;
} 
?&gt;


To activate debug messages, run the following drush command:

drush -y vset foo_debug 1


And run watchdog messages in foreground before your test:

drush watchdog-show --tail --full


Read more:

Add hook_alter for catching and debugging the requests and responses.