As to drip timing.
I do not believe that the pump element check valve can be removed on most late pumps. If I'm right one can not get good drip timing results. We purchased the high pressure method about twenty years ago so I can't say for sure. We also have the Snap-On timing adapter so that timing and rpm can be checked with a light.
The high pressure method just uses about 400psi to overcome the pump element check valve so beginning of delivery can be tested like it was done with a drip timer.
Bosch Master, ASE Master, L1
33 years MB technician