Sprinter 211 Sporadic no power/regulates

Servus, following situation, Mercedes Sprinter 211 CDI Bj 2000 Idle full throttle sometimes it runs only up to 3000 regulates. when driving the same, sometimes it has no power, you drive in the 2nd gear, it accelerates up to 2500 then as if it regulates, you stay on the gas then after a short time it passes over and has full power again. At 100 km/h if you give full throttle the same, no e-power, then again full power. Turbochargers, pressure converters are already new in the vehicle. Tomorrow I let you read out. Does someone happen to have such a problem? Brake light switch works so far, can it still lie on the part?