Oh you mean the search performance, that’s a different situation.
In case the ajax response is slower, then I recommend reading these chapters in the documentation:
– Fine tuning search performance – very important adjustments, expecially for shared and managed hosting packages
– Performance tuning – explanations about search performance and expectations and factors slowing down the plugin.
Long story short, the plugin speed and performance more-less corresponds with the hosting server performance if properly configured. (except cases where some kind of error causes the slowdown)