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.