Draw vacuum from both runners if you can. To stop the fluctuations in the guage, simply squeeze the line to restrict the flow of air. Use a fishtank air line clamp if you have one. Squeeze the line just enough to dampen out the pulses so that the guage reads smoothly.

It sounds like the adjustable unit is the way to go, but i highly recomend that you buy a factory manual & have a good read up on the parts that tell you what you should expect from this trans. It will also tell you how to fit the modulator.
Like I keep on saying, the manual should be the FIRST piece of performance equipment that one should get. It saves so much angst & grief.