Actually its the throttle shaft bushings that wear out and he air goes out the side of the TB. The spring side bushing near the return spring wears out first because more load.Throttle body spring leak seems to be normal on older cars because a lack of seal between the spring and the Throttle body.
I bought bushings from darkcat, he might have more. Also in the bottom of the brass "sleeve" is an o-ring. Replace that if the rtv fails.Status update: I gently pulled out the P444C line by pushing it up and down and it came off without breaking anything. I can confirm after reading this forum: vacuum clips on upper vac lines, going into UIM?
That it is held in by a black plastic piece that's surrounded by a gold or brass cover. You can slightly pull out the plastic piece with your finger nail and try to apply RTV sealant. I just need to find a tooth pick to spread the sealant and it's supposed to take 24 hours to cure. I will try it again soon.
Anyways, this vacuum leak also explains why this engine becomes easily heat soaked since it's sucking hot air directly from the top of the engine bay. The intake manifold valves open at 4000K+ rpm and that's exactly when it struggles to accelerate on 90+ degree days. Once this issue is fixed I'm hoping this Cougar will perform better.