Since fitting the exhaust the bike definitely runs better, feels less restricted, just a bit of surging at low speed constant throttle. If a free flow air filter and a specific o2 setting will smooth this out this will be fine for what I want, I have fitted new chain/sprockets and the inner tube cush drive mod so that should help as well, I just want the bike to run as smooth as possible without being obsessive about max bhp, �60 for an air filter is 'kin stupid!! if I want more power I will take the GS.
Thanks for the information.

Al.