Map sensor is that little black feller right in the front/center of the throttle body.

 

So you think maybe it's faulty? And does having headers on there change the readings?

 

Headers won't affect MAP. But, you were getting some strange readings on the logs...... not entirely sure what that is all about. There may just be a nipple and O-Ring for it's vacuum source....

 

Wanted to leave an update - Took it in to a reputable mechanic and transmission shop yesterday and he called me last night and said it needs a new ECM. The one in there is from a 1996 and he said 96-97 were different and he couldn't get any accurate readings. The strange thing is the guy I bought it from put that ECM in there and had it flashed to his VIN and said he drove it for about 2 years with no issue. The mechanic said he tried another ECM from another truck that had other issues and it seemed to fix the issues I'm having.
I would never have thought that was the issue but I'll have to go with his suggestion and try it. He sees dozens of trucks a week and knows more about the truck already than I do.
I'll continue to update as I find out more!

 

96 PCM in a 2000 truck shouldn't work at all... It may run the engine, but, trans sensor are different, and on 98 and up trucks, ALL of the gauges are driven by the PCM...... I fail to see how that could possibly work.