they are cheap to just replace. and they are known for going bad. did u check the resistance hot and cold? dont remember the exact values but last time i had them i found them on a google search.
a bad fuel pressure regulator can also cause a rich condition, along with any type of leaking or seepage on the fuel lines.
I checked it at cold then let the truck warm up a little and checked to see if it changed. It changed as it warmed so I was thinking it's ok. I'll probably just replace it anyway later on. Found these on here I think.
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