I noticed I was leaking coolant and I stopped and then realized the tube coming out of the intake manifold, which connects to the heat core inlet, is broken. The broken part is part of the manifold so I need a whole new manifold.

Is there any perforcemance manifolds for our cars? I think just go to the junkyard to find a use one but its alot of work to take it off.

 

I think you are correct and stuck finding a 3.1 manifold.
Shouldn't be too difficult a search!
But no, no "performance" swapping able to be done.
AND I would take off your current manifold first to make sure which ever option you score has all the stuff your original manifold has.
PS a 3.1 has more stuff than a 2.8! on it! Exactly what fittings or vacuum "things" to me not known but stick with your 3.1 search & you will do fine.