I was all set to go on this one until question number 4 slapped me in the face.
How can a technician with a conscience give advise to anyone who could ask question number four. There is safety and other issues here.
As a result my only answer is that the current (since 1985) low pressure switch is also a high pressure switch. It handles both issues. MB# 124 821 36 51 or 124 820 80 10. Both numbers are from memory I might be wrong about the second one. These are both the same part from different vendors and are interchangable.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician