From the video (I think Tiberius made that video):
Time Crisis 5\TC5\Engine\Config\BaseInput.ini
line 37 from Bindings=(Name="MouseX",Command="Count bXAxis | Axis aMouseX") to Bindings=(Name="MouseX",Command="Axis aMouseX Speed=0.05")
line 38 from Bindings=(Name="MouseY",Command="Count bYAxis | Axis aMouseY") to Bindings=(Name="MouseY",Command="Axis aMouseY Speed=0.05")
instead of 0.05 and 0.05 I used 0.03 and 0.015
for a 16:9 1920x1080 screen