Can I use Inteligent Agent?

I have 8.0.5 databases on Linux. i can't install Inteligent Agent 8.0.5...
Can I use Inteligent Agent for example 8.1.6 ?

Yes you can.

Install the OIA into a separate $ORACLE_HOME.

When installing the 816 software, first deselect everything.
Afterwards you can just select the OIA and dependent software.

Hope this helps
Gert