I'm getting around 12" entering my blue vac amplifier on my 85 300TDT, only getting under 5" to my trans. When its cold the needle on my mityvac doesn't move when I increase throttle. Could a bad vac. amplifier be my problem? Has anyone heard of them going bad. I understand they are only on 85 and above model. Thanks PS I'm getting a reading of 20" off of the main line. This problem only occurs when theoutside temps go below freezing. ????

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85 300TDT 456,000 orig. miles