on a 98 SE, yes I know how to work it

First the quickest and easiest vacuum leak to find is the line that goes from the TB or just behind it to the firewall into a box next to the brake master cylinder. If often gets knocked off when doing spark plugs and such in the back. That box is the vacuum reservior the HVAC uses to control the directional valves.

You can skip over John'* advice. While it'* good information..it only applies to 92-95 model years.

Most likely you have collapsed nipples.

http://www.bonnevilleclub.com/forum/...ght=hvac+vents

It'* a long read, it'll walk you through the diagnosis steps one by one..and then on page 6 if you still don't have vents... fix the collapsed nipples.

Whoopsie...