There is only one pressure regulator. The other device that looks similar (but with only two hose connections) is a dampener (for noise).

I like your open checkbook approach to diagnostics. To bad the thought of paying a competent technician usually never comes to the mind of those using such diagnostic techniques. This work is so easy.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician