Originally Posted by TwitchKitty

The next item downstream would be the valve on the firewall that has an electrical and an air pressure component to it. What controls the electrical part of that valve? Does that valve pass the manifold pressure to the ALDA or is there vacuum somehow involved?

Is that called the crossover valve? Is it controlled by the overboost sensor? Is the overboost sensor on the intake manifold?

I have read a lot of threads on this but different views are expressed and I am not sure how this system really works. I promise to read about it in the manual someday.