diff --git a/src/CurlClient.php b/src/CurlClient.php
index 364b34d..cc6d5f4 100644
--- a/src/CurlClient.php
+++ b/src/CurlClient.php
@@ -20,6 +20,9 @@ class CurlClient
     const HTTP_ERROR = 500;
 
     const RATE_LIMIT_RESET = "x-rate-limit-reset";
+    const RATE_LIMIT = "x-rate-limit";
+    const RATE_LIMIT_REMAINING = "x-rate-limit-remaining";
+    const DEFAULT_RATE_LIMIT = 180;
 
     /**
      * @var array of headers sent with HTTP requests
@@ -27,18 +30,48 @@ class CurlClient
     private $_requestHeaders = array();
 
     /**
+     * @var array of headers received with HTTP responses
+     */
+    private static $_responseHeaders = array();
+
+    /**
+     * @var bool keep the request rate below the API rate limit
+     */
+    private $_keepBelowRateLimit;
+
+	/**
      * @var array of extra CURL options
      */
     private $_curlOptions = array();
 
+    /**
+     * @var bool log curl requests and responses
+     */
+    private $_debug;
+
+    /**
+     * @var string file name for curl debugging log
+     */
+    private $_logFile = '/tmp/curl_data.log';
+
     /**
      * @var int the last HTTP status code received
      */
     private $_lastStatusCode;
 
-    public function __construct($apiKey = "", $siteID = "")
+    public $MockCurl = false;
+
+    /**
+     * Array key should be part of the URL to which the response belongs
+     * @var MockCurlResponse[]
+     */
+    public $UrlMockResponse = [];
+
+    public function __construct($apiKey = "", $siteID = "", $keepBelowRateLimit = true, $debug = false)
     {
         $this->setCredentials($apiKey, $siteID);
+        $this->_keepBelowRateLimit = $keepBelowRateLimit;
+        $this->_debug = $debug;
     }
 
     /**
@@ -196,6 +229,11 @@ public function httpRequest($requestParams, $url, $method, $requiredParams, $opt
             return false;
         }
 
+        if ($this->_keepBelowRateLimit)
+        {
+            $this->_checkRateLimit();
+        }
+
         if ($options &&
             is_array($options) &&
             array_key_exists("headers", $options) &&
@@ -274,22 +312,97 @@ function($curl, $header) use (&$headers)
                 return $len;
             }
         );
-        curl_setopt($curlHandle, CURLOPT_TIMEOUT, 60);
+        curl_setopt($curlHandle, CURLOPT_CONNECTTIMEOUT, 30);
+        curl_setopt($curlHandle, CURLOPT_TIMEOUT, 60 * 2);
+
+        if ($this->MockCurl)
+            $result = $this->DoMockCurl($url, $method, $headers);
+        else
+            $result = $this->DoCurl($curlHandle, $requestParams, $headers);
+
+        unset($this->_requestHeaders["Content-Type"]);
+        return $result;
+    }
+
+    private function DoCurl($curlHandle, $requestParams, $headers)
+    {
+        /** ********** DEBUGGER ********** */
+        if ($this->_debug) {
+
+            // capture the PHP output
+            ob_start();
+            $out = fopen('php://output', 'w');
+
+            curl_setopt($curlHandle, CURLOPT_VERBOSE, true);
+            curl_setopt($curlHandle, CURLOPT_STDERR, $out);
+        }
 
         $result = curl_exec($curlHandle);
 
+        /** ********** DEBUGGER ********** */
+        if ($this->_debug) {
+
+            /** @noinspection PhpUndefinedVariableInspection */
+            fclose($out);
+
+            // get the curl output
+            $data = ob_get_clean();
+
+            // insert the request parameters sent
+            $data = preg_replace('/(\r?\n){2}/', "\n\n$requestParams\n\n", $data, 1);
+
+            // append the response received
+            $data .= "\n\n" . $result . "\n\n";
+
+            // write to a log file
+            file_put_contents($this->_logFile, $data, FILE_APPEND);
+        }
+
+        self::$_responseHeaders = $headers;
+
         $this->_lastStatusCode = curl_getinfo($curlHandle, CURLINFO_HTTP_CODE);
         if ($this->_lastStatusCode == self::HTTP_RATE_LIMIT)
-        {
             $result = $this->retry($headers[self::RATE_LIMIT_RESET], $curlHandle);
-        }
 
         curl_close($curlHandle);
 
-        unset($this->_requestHeaders["Content-Type"]);
         return $result;
     }
 
+    private function DoMockCurl($url, $method, $headers)
+    {
+        /** @var ICurlResponse $response */
+        $response = null;
+        $return_key = '';
+
+        // look for a mock response that matches the URL
+        foreach ($this->UrlMockResponse as $key => $value) {
+
+            // does this response match the requested URL?
+            if (!str_contains($url, $key))
+                continue;
+
+            if (strtoupper($value->Method) == strtoupper($method)) {
+                $response = $value->Response;
+                $return_key = $key;
+                break;
+            }
+        }
+
+        self::$_responseHeaders = $headers;
+
+        if (empty($return_key))
+            return '';
+
+        $this->_lastStatusCode = $response->HttpCode;
+
+        // remove this response from the stack
+        unset($this->UrlMockResponse[$return_key]);
+
+        // return the value
+        return $response->Content;
+    }
+
     /**
      * @brief get the last HTTP status code received
      *
@@ -325,4 +438,48 @@ public function retry($wait, $curlHandle)
         $this->_lastStatusCode = curl_getinfo($curlHandle, CURLINFO_HTTP_CODE);
         return $result;
     }
+
+    private function _checkRateLimit()
+    {
+        // If no API calls have been made, no need to delay.
+        if (empty(self::$_responseHeaders))
+        {
+            return;
+        }
+
+        // Default the $limit and $remaining values if not set in the last response header.
+        /** @var int $limit */
+        $limit = isset(self::$_responseHeaders[self::RATE_LIMIT])
+                    ? (int)self::$_responseHeaders[self::RATE_LIMIT]
+                    : self::DEFAULT_RATE_LIMIT;
+
+        /** @var int $remaining */
+        $remaining = isset(self::$_responseHeaders[self::RATE_LIMIT_REMAINING])
+                        ? (int)self::$_responseHeaders[self::RATE_LIMIT_REMAINING]
+                        : self::DEFAULT_RATE_LIMIT;
+
+        // If no API calls have been made, no need to delay.
+        if ($limit == $remaining)
+        {
+            return;
+        }
+
+        // If we are below 5% remaining, sleep for 0.50 seconds.
+        if ($remaining / $limit < 0.05)
+        {
+            usleep(500000);
+            return;
+        }
+
+        // If we are below 10% remaining, sleep for 0.25 seconds.
+        if ($remaining / $limit < 0.1)
+        {
+            usleep(250000);
+        }
+    }
+
+    public function setLogFile($fileName)
+    {
+        $this->_logFile = $fileName;
+    }
 }
diff --git a/src/ICurlResponse.php b/src/ICurlResponse.php
new file mode 100644
index 0000000..4987dc8
--- /dev/null
+++ b/src/ICurlResponse.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace OntraportAPI;
+
+/**
+ * @property string Content
+ * @property int HttpCode
+ * @property int ErrorNumber
+ * @property string ErrorMessage
+ */
+interface ICurlResponse
+{
+}
diff --git a/src/MockCurlResponse.php b/src/MockCurlResponse.php
new file mode 100644
index 0000000..d3f2b4a
--- /dev/null
+++ b/src/MockCurlResponse.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace OntraportAPI;
+
+class MockCurlResponse
+{
+    public string $Method;
+
+    /** @var ICurlResponse */
+    public $Response;
+
+    /**
+     * @param string $method
+     * @param ICurlResponse|mixed $response
+     */
+    public function __construct(string $method, $response)
+    {
+        $this->Method = $method;
+        $this->Response = $response;
+    }
+}