Hi Johntread,
Thanks for answering that fast.
I don't know about what system are you talking about. the engine type is#612963. I don't know if that number tells you something, there is nothing in the handbook about system.
Tomorow I will go under the hood and look on the sensors in the rail and fuel pump, also will ask a friend to take a couple of pictures in order to send it to you.
I forgot to say that some times the full power return and the engine develop the full speed, but after a while, without notice or enything that can be related with, the power decrece to more or less 2500 rpm.