going back to the very early 80s yamaha had YICS on some of the bike which linked the 4 cylinders with a channel in the cylinder head,that worked on those engines as the channel was 10mm and it was near the ports,the idea was as a cylinder was on induction it would drag some mixture from the othe carbs,this would cause swirl within the combustion chamber giving better combustion,it did work on those engine because they were 8 valve,a modern 16 valve or 20 valve engine has natural swirl in the combustion chamber and a better combustion chamber shape so the linking of the ports wont work,and as the pipes are in the inlets they are too far away anyway.yamaha only ever fitted YICS on one multi valve engine and that was a v twin XZ550,that was by pipes and it did not work on that either