I noted in the jetting section the installation states :

"The solenoid jets are still utilised in the Jha and HRC kits but now modify auxiliary airflow through the carb's. The Y joint is a direct replacement for the standard piece, with the straight side going to the solenoid closest to the frame. The + joint should have the rubber cap removed and the side with the jet left open to air. The 2 smaller joints go to the carb's, and the last joint goes to the pipe adjoining the Y joint."

I think this may be for the mc21 configuration. I found a paper online specifically for mc28 that says the rubber cap is to be left on, the jet end left to open air, one end to the Y joint and the other end to the carbs. I suspect this is because on the carb end there is another T fitting that splits and goes to both carbs. I'm wondering what others have done on the mc28. Perhaps there is an option to remove that small T and tie each carb to the + connector. This would indeed have a minor change in the airflow.

I am wondering if this is impacting my slow speed. Ironically today i was out riding and i was again unable to clear it up with the mixture screw.

I knew when i bought the bike I`d pretty much be on my own . More research is clearly needed on my part. The good thing is that i am almost there.