Power valves. Some say half your manifold vacuum, some say 2 hg below. Who is right?
I read an article where a vacuum gauge is installed in the car and you use a narrow band O2 moniter. You cruise around in your basic operating rpm checking your gauges. Keep a record of your range of vacuum levels from regular driving. You want your PV number below these levels. The A/F ratio will be at 14.7:1 at cruise to 12.8:1 under power which is when the PV opens.