Thanks Jim, I'll check out the vacuum system.
I did move a bunch of stuff around when I was removing the vacuum lines to the EGR valve solenoids.

It looks like on my SDL the small line from the vacuum pump goes to a 4-way connector and then there is a line to the proportioning valve on the injection pump, then over to the blue amplifier then the changeover switch (square top unit on bulkhead?) and then I guess to the transmission vacuum modulator. Where is the vacuum modulator located ?