MKL starts “rolling” and goes off again when accelerating

Good evening! Had my Omi now 2.5 weeks in the workshop. First the problem was that the emergency program incl. MKL approached during the acceleration. After replacement or checking of exhaust gas return valve, pressure hoses, speed sensor and air quantity meter he was released today as healed. On test drive from workshop everything was OK. Now the problem has turned around: If I am at the intersection (Standgas) the MKL & emergency program starts, then I slip slowly and at some point, we nn he comes on the road and I finally come at higher speeds (from about 2000 – 2500) , the MKL goes out and he runs as if nothing was. Maybe any of you have an idea??? Am despairing! Greetings Maik