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I didn't read about it yet in this thread so I'd suggest checking the intake elbow (that curved bellows) attached to the throttle body. They crack on the bottom in the crevasses where you can't see causing driveability nightmares such as yours. Dorman offers a Chinese replacement that, IMO, works well ('cause I have one on my truck). Thirty-five bucks from Rock Auto.
One of the first things I checked. No cracks and intake is sealed properly. Thanks for the reply!
Problem was finally solved, was the tube under the lower intake manifold that runs coolant to the temp sensors. It was completely clogged. Installed a new one and problem was gone!