Give me a link to your project specify what sprite and what script and I'll try to find a way to make your script faster, if you want multiple scripts to be sped up specify them all! Speed that I add may be minor changes or major, it depends on how simplified your code already is..
I'll try my best to make your laggy projects even just a tiny bit faster! And even if your project isn't that laggy it is still good to simplify code for when you add to it later and there is more that scratch is running! Though If I don't see any way to speed it up then I'll just let you know..