The voltage will never be constant at 3.6
When the solenoid is closed, boost will rise, when it opens, boost will drop. So in reality, it's always, on, off, on, off, etc once it gets to that point, so the voltage will always be above 3.6, below 3.6, etc. The duty cycle will vary depending on RPM and boost.
If I incorporate hysteresis, then there might be too much time between on/off cycles, and the boost may fluctuate constantly by 1 psi or so (as opposed to looking constant)