How do i tune a 2.6ltr Astron Engine (idle mixture)

This is my first post in this newsgroup....so a big hello to everyone.

I was wondering if you guys could help me tune my 2.6ltr astron II engine on my 83 sigma....I have set the timing very carefully with a timing light, but i am still getting pretty bad emissions from the tailpipe.

My next port of call is to set the idle mixture, but i have no idea what technique to use to set it.

Does anyone know the steps to go through to set the idle mixture?

Any help would be hugely appreciated

Thanks Dan