When yo turn the carb upside down, I think you will see that the PCV should be connected to the front side of the carb, and you will see why; the passage is interconnected to both primaries. And I think you will see that if you hook it to the back, the rear four cylinders will run lean, especially the two rearmost. Oh, and that might be the source of your AFR monkey business. If your O2 sensor is in the merge or near to it, it will get all mixed up. That back port is for the power.brake booster