That's pretty much how this is, sometimes hard to detect and a little worse when hot.
Its most noticeable at sitting at lights, or when you are stationary with drivers door open, the edge really accentuates the rocking movement.
Couple of times after an 'Italian tune-up' went altogether, well at least for a few minutes.
Last time I did the DV's I noticed what looked like residue on the surface of plunger, (this is the bit that sits way down inside pump) so today pulled 5/6 out, plungers too - my intention was to swap out with OM606.962 parts which I had to hand, unfortunately all the part numbers were different so didn't risk it.
The plunger did have small build up but this looked worse than it actually was due to locating notch running up one side, from the top it could be mistaken for pitting.
Carefully re-assembled 5/6 torqued 35nm, engine eventually fired - exactly the same, no difference whatsoever.
It's getting quite sad now as not only do I know all the socket/spanner sizes, but torque values too, the above including manifold removal probably took less than two hours
