carb question with pics

[Fscott4]

disassembled carbs for rebuild. I was going checking air/fuel flow thru the nipples and noticed one of the circuits has a plug in it and doesn't flow at all. This is obviously a factory plug and I just cant figure out why its there. the other carb flows air/fuel freely thru both nipples.
Just curious to know why this is set up like it is?

 

[mikidymac]

I have never seen one plugged. They typically have a restrictor orifice to build fuel pressure to the return line. If it was actually plugged the fuel pressure would be too high and there would be no need for the return line.

 

[Fscott4]

The skis are new to me and I'm learning as I go. I see the fuel circuit goes into the first carb, crosses over to the next carb and then returns to the fuel pump. That's why this is not making sense. I'm thinking I should drill it out to allow for flow. Maybe someone put the wrong carb on at one time? not sure what to do at this point.
The ski was running but not great. Im thinking maybe it was running on just one carb