as you said, you installed the google apps. well, google apps are 100 megs. guess why. Its not just gmail and what not. It includes all the proprietary APIs, everything.

You don't get any of that in AOSP. Reinstall CM but do not installed gapps, and you'll have something close to AOSP (well, better than AOSP still)

I bet you don't last a day before you'll install gapps again (and thus all the google proprietary libs, etc.)