apache slow loading images on linux

Hi,
I've got apache and tomcat running with mod_jk & mod_ssl on linux.
When I access any webapps through tomcat the performance is fine.
However, when I load webapps from apache, the performance is dreadful, especially when there are images to load up.
I've had this running on windows before without any problems like this.
I've done the apache-optimising stuff drom the apache documentation but this hasn't made any difference.
Can anyone help me out there as I need to put this on a linux production machine asap.
Thanks