I recently had my turbo replaced at MB. Before I took her in to the shop I used to hear a popping noise as I reached the 2000 RPM while gradually accelerating on neutral. After the work was done I still hear the popping noise and acceleration is poor I was told the noise is the Turbo engaging (SOUNDS LIKE A MISFIRE). I don't feel the turbo kick in until I have depressed the gas pedal almost to the floor. Any help where this sound is coming from and if it is normal is appreciated.

Alex.