Very poor running problem

[hotmetal]

Given our relative levels of mechanical nous I would expect Mike to be right, but I also wonder if your air intake could have some blockage? I only say this as I had a similar thing a few years ago and it turned out to be an Autocom lead/connector that I stashed under the seat getting into the air intake bit under the front of the seat/back of the tank. Probably not but takes 1 min to check.