[fredmeister]

Originally Posted by Speedy Squirrel

Fredmeister, I agree with your idea, and Porsche930, it is another way to go. Even with the same pressure on the front and the back of the diaphram, there is a retard effect under boost, due to the way the springs inside the capsule bias the two pressures.

so there is a spring inside the can that biases the movement of the diaphragm when the same vacuum or boost is applied across both ports on the dizzy by teeing the line as i suggested. That is what i found from experimenting on my own unit and is why i did it. i just did not know what the internal guts of the dizzy can looked like to account for this.
To be sure if it works, I suggest that 930 porsche install a tee in the line like I suggested and apply a vacuum and then a boost pressure to the unit while it is idling to see if this works on his dizzy. You can see the effects of vacuum and then boost with a timing light and measure the advance and retard in degrees for each scenario as well to get a feel for what static ignition timing to set it to at idle and still meet the 4000rpm requirement.