Well, after changing the weight class to 8600 lbs, registering the truck commercial, etc., getting it inspected, it still shows as 0-8500 lbs, which is the original manufacturer's specs. I found out that no matter what you do to your truck here in NY, the original specs will always show at inspection, so there's no way around CEL and emission problems.

I guess I will try and change the O2 sensor, like HeyYou recommended, that is, once the weather is stable enough. Right now everything is wet and muddy and I have no garage space to work. But I will update as I go along and see if changing out the sensor again will do the trick so that if anyone else has the same problem they will have more information.