I'm not sure, but I think the unisyn needs to be the same one on both carbs! I think that the unisyn is measuring the carb its on, and placing it on the other carb enables you to duplicate it's airflow/vacuum. Using two would give you a benchmark for the other! What I'm saying is sticking to one removes a variable, and is the intended means of EQUALIZING the carb settings. I have yet to use it on my 261 dual carb, but used one on a motorcyle years ago, so I may be remembering wrong ( insert grain of salt here.)
