High cpu usage 9742, MBP Leopard 10.5.6

Hi all!

I am running 9742 in a MBP 3 GB ram, Leopard 10.5.6.
I have removed caches, launched 9742, loaded a mid size project, and cpu shows over 50%, fans sound like we are taking off! Consuming a lot of battery juice.
Attached is a cpu snapshot.

Any suggestion to easy the load will be really appreciated.

Thanks in advance,
Gustavo.