Secondary Air Valves & EVR (which has nothing to do with secondary air, but is a solenoid vacuum valve similar to the Thermactor Air Bypass & Thermactor Air Diverter, and is usually mounted beside them)
TAB & TAD solenoids should read 50-100 Ohms; each should hold vacuum applied to the source (farthest) nipple until 12V is applied across the solenoid terminals, at which point it should vent to the other nipple.
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