You need to make a Zone Definition and set the DEFINE for who is allowed the Free Shipping Options freeoptions and set it on that shipping module with the Total >= 90 ...

Next, look at what the Zone Definition value is in the URL where you will see:
zID=XX

Now, say you wanted to customize the Flat Rate flat to turn off for this Zone Definition when the order is >= 90 ...

You can add the code in RED to do this:
Code:
      if ( ($this->enabled == true) && ((int)MODULE_SHIPPING_FLAT_ZONE > 0) ) {
        $check_flag = false;
        $check = $db->Execute("select zone_id from " . TABLE_ZONES_TO_GEO_ZONES . " where geo_zone_id = '" . MODULE_SHIPPING_FLAT_ZONE . "' and zone_country_id = '" . $order->delivery['country']['id'] . "' order by zone_id");
        while (!$check->EOF) {
          if ($check->fields['zone_id'] < 1) {
            $check_flag = true;
            break;
          } elseif ($check->fields['zone_id'] == $order->delivery['zone_id']) {
            $check_flag = true;
            break;
          }
          $check->MoveNext();
        }

        if ($check_flag == false) {
          $this->enabled = false;
        }
      }

// bof: turn off for over 90 and zone 92
      if ( ($this->enabled == true) ) {
        $check_flag = false;
        $check = $db->Execute("select zone_id from " . TABLE_ZONES_TO_GEO_ZONES . " where geo_zone_id = '" . 92 . "' and zone_country_id = '" . $order->delivery['country']['id'] . "' order by zone_id");
        while (!$check->EOF) {
          if ($check->fields['zone_id'] < 1) {
            $check_flag = true;
            break;
          } elseif ($check->fields['zone_id'] == $order->delivery['zone_id']) {
            $check_flag = true;
            break;
          }
          $check->MoveNext();
        }
        if ($check_flag == true && ($order->info['total'] - $order->info['shipping_cost']) >= 90) {
          $this->enabled = false;
        }
      }
// eof: turn off for over 90 and zone 92

    }

// class methods
Change the 92 to match your zID ...

Then adapt that to your other shipping modules ...