I have a sprinter 316 and stand up

Hello, I have a problem and it is very fat because it has already taken to 2 workshops and they do not find the problem. It turns out if I go at an adequate speed and without forced the engine for overtaking or outputs is going well but when I squeeze it a little for some extreme case after a while I stop the engine and I have to throw myself into the gutter and wait a while to get back again, and if I go out very strong, it will stop getting to the destination again. Please if you can help me, I thank you. all the best