In the Preferences > Engine(tab) there’s an option to Bypass processing when detecting CPU overload. Have you got this option enabled? Unchecking it, by the way, may not be advisable as maxing out CPU produces audio dropouts. The playback cursor also halts, along with audio ceasing, when CPU overload occurs.
i also believe that Podium Free is limited to one processor core, therefore doesn’t fully utilize your system’s processing power.
Not sure what you mean by “a plugin… was removed”. Podium may disable a plugin, in some circumstances. Projects also maintain references to plugins, even if they are no longer on hard disk.