Thank you Andy for your advice . But after reading posts and the tuning bit for the last few hours ,I think I'll buy some Swarbrick end cans ,leave the holes and get the bike Dynoed. I have a set of new rings with a great set of std barrels and pistons to go on ,Should I swap them over now ,run it in with the holes coverd and the wires connected , then get it Dynoed ? Thanks again