TB Idle circuit

So I have been doing the carbs (agin) on Piere Luc's Triumph Thunderbird and one of the pieces of information I was missing was whether the idle mixture screw adjusted the idle fuel or air flow. Important to know as you need to screw these in or out dependant on whether you are rich or lean at idle. The symptom I am still getting is that the engine still hangs onto revs. a little too long to be confortable riding. this turned out to be lean running at high rpm so I went down on main jet sizes and put the needles back on the middle clip, but now I still get the symptom at idle low revs. I found one reference on the internet and decided to take the plunge and screw the richness needles in another half turn to 1.5 turns, in the hope of leaning it out - this would imply that you are restricting fuel to the idle circuit and therefore leaning it out! In the hope that I went the right way. So now I am on 97.75 main jets and 3 x 40 idle jets at middle slot for the needle clips. All the jets are not Mikuni and were purchased at WEmoto.fr. I am going to rebalance the carbs. and take it for a spin. Be back later with the results.