Why might VCV as a VST use much more CPU than as a stand-alone?

I was playing with Omri’s Glass Pane patch and I wanted to jam to it so I opened it as a VST in Ableton and not a chance. As a stand alone it was maybe maxing at 75% but as a vst it was way up above 120-150 and totally unusable. Since I have two computers going here, I took out anything he had in there that was just sound FX (only 2 tracks really) and pared down the 16 track MindMeld Mixer and Aux module to the 8 channel version. On it’s own it’s barely hitting 35% but in Ableton I see it still bumping100 - 120% occasionally, especially when anything else occurs and the computer needs a chunk of CPU.
Any cure or mitigation for this?