There is an obvious size different between the original m52 inlet manifold and the M50 that has approximately 30% larger intake circumspect than the m52 intake manifold.
The larger M50 manifold will not perform as good at low Rpm's due to its size as the original smaller one that came with the engine. To cure that you have to put in larger "hotter" camshafts instead of the rather tame camshafts that are standard and re-tune the ECU parameter accordingly. If you do nothing, other than mount the manifold then around 2800 - 3200 rpm. or maybe higher Rpm's it will come alive and put a big grin on your face all the way up-to 6500 rpm.
If you change to bigger/hotter camshafts, everything begins to come together in harmony.
You can read more about hotter camshaft's with other pictures in my portfolio.
This picture was not taken by me, it was found somewhere on the Internet, therefor credit to the one who took this picture.
I used it only to illustrate the size difference between m50/m52 inlet manifold.