Load balance issue

[leap]

Hi,

I have configured load balancing and failover over two WANs successfully follow the instruction from this link http://forum.pfsense.org/index.php?topic=28121.0
I have two WANs, WAN1 speed is 4MB and WAN2 speed is 1MB. When PC1 accessing to internet it is going to WAN2, it will always going to the WAN2 and never go to WAN1.
Is there anyway that we can balance on the outgoing traffic between these two WANs. I would like all clients to be able to use both internet lines.

Please advise how I can get it to work this way

Regards,
Leap