Vac at 18 is fine. But your trans line isn't being modulated. Shift your gauge to the VCV line, which should be on the bottom of the BUFO, to the right. You can also test the turbo sense, which is the center connection. This should show manifold pressure (not vacuum).

If you have modulated vacuum at the VCV line, then the BUFO isn't working correctly. If you don't have vacuum at all, then the line is open, track it back to the break. If it doesn't modulate, the line is either clogged or the VCV is bad or misadjusted.