Cubase 7.0.7 Ram and VST Performance

Dear fellows,

I’d like to know what is going on with the VST Performance in Cubase 7. I never had hard issues but sometimes I get about 40% of load with a very small amount of tracks and plugins, although other project have a lot more complex mix and is about the same. I have a professional Recording studio and I am working with specific project setups often

88.2/32bit with a mac pro 2009 with intel xeon 2x quad core and 16gb of memory (until 3 days ago a had 6gb). So I fianlly found Ram to update the machine, but nothing better actually happened. Is there any secific reason? I am runing 10.8.5 OSX aon an SSD 240gb and my records are written on an WD HDD 1TB