The way that vacuum causes no shift is by not being there at the modulator. You need to use the gauge hose set up in the article (or reasonable facsimile). You need to tee it at the modulator (hard way) or at the first junction the hose ends at near the valve cover (easy way - same vacuum).
For test purposes try hooking the source line straight to that line giving full vacuum all the time. The car should shifts bing, bing, bing and probably slip all over the place. If this is the case vacuum somewhere inbetween is the answer. If you are good, lucky, and tenacious the article will have you adjusting it sweet.
Bosch Master, ASE Master, L1
33 years MB technician