An exhaust shop here in Ft. Worth fabricated my exhaust from the turbos all the way back, so yes, it can be done. Mine is made of aluminized steel and is pressure bent, so it doesn't flow quite as well as a mandrel bent set up and isn't as pretty, but it made a huge difference.
Supposedly, you should be able to pass emissions with just the main cat. You should drive your car around for a little while prior to getting it tested just to get things nice and hot.
Hope this helps.
h82luz