It has been a year, you probably have solved this, but someone may still need.
I had the same problem so I checked the lib-syndication.php
Find this line (line 371 in 1.4.1):
PHP Formatted Code$fulltext = stripslashes( $row['introtext']."\n".$row['bodytext'] );
remove the bodytext part:
PHP Formatted Code$fulltext = stripslashes( $row['introtext'] );
seems to work for me.
Make sure you backup your original file so that you can go back. Also, one could probably make a $_CONF variable and add the option of having whole body or just the intro.