Originally Posted by andrewcologne (Post 11971910)

the "tricky" thing is, that many 123 users do simply use the known "ported" vacuum connection which leads to the dizzy. And here this gives a total wrong signal as ported vacuum is only available at a slightly open throttle. With this kind of vacuum you will never get the whole "common" map vacuum range needed for a proper timing at "all loads".

So ... To get a full map signal ...
For 911 sc till '79 without ecu this is the same vacuum line like connected to the wur.
For 911 sc from '80 with ecu its the same vacuum line connected to the cruise control and deaccel. Valve.