Using Sharepoint 2013 Search.asmx with FQL

Question

I have a website using sharepoint search services to query SP index. After migrating to 2013 I started getting this error:

ERROR_BAD_QUERY

Error: We didn't understand your search terms. Make sure they're using proper syntax.

Here is my Query XML:

<QueryPacket xmlns="urn:Microsoft.Search.Query">
  <Query>
    <Context>
      <QueryText language="en" type="FQL"><![CDATA[string("TEST", mode="and") AND filter(contentsource:equals("MyContnentSource"))]]></QueryText>
    </Context>
    <SupportedFormats Format="urn:Microsoft.Search.Response.Document.Document" />
    <ResultProvider>FASTSearch</ResultProvider>
    <Range>
      <StartAt>1</StartAt>
      <Count>10</Count>
    </Range>
    <TrimDuplicates>false</TrimDuplicates>
    <Properties>
      <Property name="Rank" />
      <Property name="Title" />
      <Property name="Size" />
      <Property name="Path" />
      <Property name="Description" />
      <Property name="Teaser" />
      <Property name="Write" />
    </Properties>
  </Query>
</QueryPacket>

I tried to run the query with type="KQL". It does not complain about anything also does not bring back anything...

what is the fastest way to fix this problem? I would rather not try to change the Query Type...