It seems to be hit or miss with the model # and the engine it goes on. I have an older non-HP 9375 1050, this seems to be the best out of the box in terms of metering on a single 4 engine even though it is supposed to be a 2-4 carb. My brother has an HP 8896, with the intermediate air bleeds removed it works OK, but we have not had O2's on it. My 8896 never worked right, I started to do the conversion, but ended up converting a 1250 instead and works great. If you read the threads, Tuner explains the origin of the 3rd circuit. There are instances where it helps and can be made to work, for most bracket cars it just complicates things. But everyone has to have newer and more, thinking 3 circuit has to be better than 2. Just doesn't always work that way.