Flash getting a small "budget"

My Flash game is really resource-demanding. It lags because it can only use up to 30% CPU for some reason.

I checked with Adobe Scout and it shows that the budget line is low.
The things that lag in the game are the vector graphics (according to heatmap at least).

This can’t be a simple threading issue either, because when measuring with Task Manager, Core 1 is running at 80%, not 100%.

What’s really weird is that when I disable hyperthreading, then the game uses 50% CPU, but lags exactly the same as when using 30% with hyperthreading on.

Why is Flash unable to use more than 30% of my CPU? Is there a way I could fix that?

I tested in Firefox and Internet Explorer on my Core i7 860 2.8 GHz, 12 GB DDR3, running Windows 7 x64