The only thing I can see in your testtag.php file that matches the gust speed is the $humidexcelsius figure, but when the page first loads it show as 1mph.
Looking at the clientraw.txt (more likely cause) it could be one of the following as they all have the same figure when I looked:
Field 045 - Humidex (in °C)
Field 075 - Max Humidex (in °C)
Field 146 - Hr Wind Dir 01