I have at last solved all the problems I had with fuel delivery. I fitted a Pingel fuel tap and turned it so the outlet faces towards the back of the bike, I also turned the fuel inlet "T" upwards so the fuel line connects from above. This set up gives me a fuel line not much more than 6 inches long, and it tucks up neatly under the bottom rim of the tank. I thrashed it up the motorway today, all the way from the Forth road bridge to Perth and back again with no sign of the power dropping off. At the moment I am relying only on the gauze filter on the Pingel fuel tap, and I have not fitted an in line filter. That said my tank is almost like new inside with no signs of rust or debris, I think it was treated with some kind of sealant when it was new.