User blog comment:Dragonjet/KC3改/@comment-27220560-20160305033802/@comment-26336961-20160307073237

Well different systems can behave in many different ways, (sometimes unpredictable or even unprobable) based on so many things software or hardware side so it's not "impossible" that kc3 causes slowdowns for you for some reason.

That said, no kc3 in itself does not inherently cause any slowdown, not is it system heavy enough to cause it on an older machine. But maybe your system or brower get's bottlenecked a bit when using it causing slowdown, check if you do not have some anitivirus or page blocker or something that isn't messing with it. Test with and without it a different times, maybe do something that you can time like a simple 3-2-A sortie with a stopwatch timer to make sure if there is an issue or you are imagining it.