Prevent CSS/JS query hash when preformance is disabled
Here's the solution (theme based) in template.php

function MYTHEME_process_html(&amp;$vars) {
  if (variable_get('environment') == 'development' &amp;&amp; !stristr($_GET['q'],'flush-cache')) {
    $vars['styles'] = preg_replace('/\.css\?.*"/','.css"', $vars['styles']);
  }
}


NOTE: This assume you have an environment setting in your settings.local.php file like so...
$conf['environment'] = 'development'; or $conf['environment'] = 'production';