That's correct. The new Host API uses ad units (aka ad slots), so you'll need to make sure both of these properties are correct, and that the ad unit in question matches the sizes described in the template as well.
Also, don't forget google_ad_host for your revenue share!
Here is some sample generated code:
<script type=\"text/javascript\"><!--
google_ad_client = \"ca-pub-xxxxxxxxxxxxxxxx\";
google_ad_host = \"ca-host-pub-yyyyyyyyyyyyyyyy\";
/* Ad Unit x */
google_ad_slot = \"zzzzzzzzzz\";
google_ad_width = 200;
google_ad_height = 200;
//-->
</script>
<script type=\"text/javascript\"
</script>
Cheers,
Sérgio
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Sérgio Gomes
Developer Relations
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