stays the same all the way to the top. I didn't retard or advance the timing at all. It produced the best power curves. When the stock ECU shifts timing points, it causes some interruption in the timing sequence and I suspect that for a couple of crank revolutions the timing is in a state of limbo while the ECU interpolates the points. I'm not positive on this, but I have found that when the timing remains the same through the RPM and load band at peak boost, it runs much smoother.