I used to have a working project at http://beta.scratch.mit.edu/projects/10106486/#comments-12712745

Usually, it calculates how fast your computer goes, but somehow the project started performing lower. My original score was 91, but one day it went to 38, and soon enough it went to -27! What's going on?

well one problem is using turbo mode
as it decreases the frame-rate and boosts caluclations