Grand Prix 125
Join Date: Sep 2012
Location: Albany, Western Australia
I can't help with the problem you describe but I don't believe it's related to MAP tubes. At the speeds you mentioned the engine will be turning ~3000 rpm. From my experience on my 2010, leaking tubes cause problems at idle and poor throttle response below 2500 rpm.
You can see a drawing that shows the MAP tubes on bikebandit.com. Each tube consists of 5 pieces, 3 rubber connections and 2 hard plastic tubes. Do yourself a favor and get rid of the stock Triumph tubes and replace with single piece flexible tubing and tube clamps at each end.
Thanks jaknife, sounds like sound advice
Die hard LT owner - you have to be with all the issues mine has had. :-)