I have the exact same problem with my GN. Been going on for a while. At first it would be fine and then start. I would find a broke Vacuum line or Vacuum connector. That happened like 5 times and finally It continued to happen and this time it was a cracked spark plug. Ran fine once and then started doing it again. Now it's been doing it worse then ever. Right about 10psi-14psi and it's predictable. Zero KR and O2's pretty much fine. I haven't even started the process of elimination on parts yet. But I see some good suggestions in here I would like to try.