I think the first thing I would do is remove the glovebox liner and remove each vac line one at a time from the switchover valve and check with an auxilliary vac source. If there are any of these lines leaking you have a bad vacuum pod. If the recirc vac pod is bad you will get 60 degree or hotter air at the vent even with a properly charged a/c.

The 134 conversion is much less than ideal in these cars, but with those pressures it should be cooling better than warm air. A thermometer in the vent for a temp reading would give us more data.