Is the PERFORMANCE 25MM PLENUM SPACER for Holden V6 VS-VY also suitable with my Ecotec V6 as its not supercharged or anything, just extractors, 2 1/2inch exhaust, memcal upgrade and CAI?

Yes the plenum spacer is suitable for your ecotec V6. In saying that we suggest buying and fitting the manifold insulator before the plenum spacer. the plenum spacer is a good supporting mod for the manifold insulator. You can find more information on the manifold insulators here:

http://support.maceengineering.com.au/Knowledgebase/Article/View/4/0/what-advantage-is-the-25mm-manifold-insulator-over-the-12mm