the only black wire with a yellow stripe i see is coming from the temp sensor on the gooseneck at the intake manifold and it goes to the box on the fender well. is this the device box you refer to? i checked the list of 4x4 wire mitsubishi abbreviations and could not find MCS. what is it. is the device box the silver box on the fender well with all the vacuum lines and wiring input? also no one made reference to the advance setting. is the black and yellow wire connected solo or on a multiwire plug?
what do you mean two coolant temps? are you saying to put in a higher temp thermostat? the engine is running in the bottom 1/4 on the dash temp guage and this troubled me as it might not be hot enough to get good combustion. the O2 sensor was replaced when i bought the cat so it should be good and is an expensive pain to relpace on a guess $60