Meaning you'd need an X pipe or H pipe to get the benefits of using an O2 AFR set-up?

 

You're correct of course, but that's usually how it's done. The sensor display is basically the average of 4 cylinders - 2 from one side, 2 from the other, they are usually installed after the collector, before any crossover. It is important to keep in mind, each cylinder will receive a slightly different fuel charge, especially in a carbureted engine. The leanest cylinder in the engine sets the lean limit for the whole engine. Ideally, each cylinder would have its own O2 sensor. Kinda spendy.

True dual ex. on my slick, thought about getting a bung installed in both pipes - and swapping over to check - but it hasn't seemed necessary. Tuning went great. Even with an O2 wideband setup still have to inspect plugs, and use your best judgment. Regardless of the indicated AFR for example, if you're seeing lean surge on the highway, it's too lean. If plugs are fouled, it's running rich, etc. Sometimes people place too much emphasis on the numbers and obsessing on that stuff. Not having to worry so much about roasting a valve while experimenting with carburetor tuning was nice, that's the benefit in my mind. I could really gain a better understanding of how each carburetor circuit works while jetting down, swapping in different power valves, and seeing how even very slight changes in tuning makes big changes in the AFR.