Magento addAttributeToFilter with Mutliple Select

The solution is to use a 'Finset'  query such as:

$this->_productCollection->addAttributeToFilter("make", array("finset"=>"38"));

A discussion can be seen here: http://www.magentocommerce.com/boards/viewthread/201312/

And a list of different options: http://www.magentocommerce.com/knowledge-base/entry/magento-for-dev-part-8-varien-data-collections