There is a metal link rod from the plastic throttle cam on the side of the engine. On the end is a grey plastic ball link. The metal rod can after a few hours slide into the plastic ball link and limit the travel of the rod when at WOT. I had this happen on my 115 and lost a fair bit of top end as a result. The dealer I took it to pulled the rod out about 5mm and then epoxied it in place which seemed to do the job. There could also be other linkage and cable related problems that could cause this I would make sure it is all set up right as well.
Also worth checking you have the latest software map etc.
Its worth posting on here if you have any E-tec questions