I assume he'* talking about ACC. 92-95 Bonnevilles had active ELC at all times. I believe in 96 you must be in ACC in order for it to work. I might be off on the year.
A mild leak can be easy to fix, by simply introducing some light oil into the system at various points. I suggest taking the top off the compressor, putting some in there, then disconnecting every connector you can get to, and squirting some in. 3in1 oil or lighter in viscosity. The oil can re-seal any leaking seals you may have.
The ultimate acid test is to do the bubbles. Like I did some time ago. http://www.williamwren.com/struts/elc.html
If your struts blow bubbles (use Snoop, or mix up your own mild soapy solution with water), like that, your ELC is going to have trouble keeping up.
In your case, it sounds almost like the vent solonoid is sticking, not only in the open position, but perhaps the closed, also. When it does open to lower the car, it may be sticking. Introducing the oil into the system can free it up. It can also help seal mild leaks in the rubber bag portion of the elc struts, not just the o-rings and seals.