Two thoughts:
(1) A "New exhaust" may mean different things to different people. Mufflers and tailpipes around my neck of the woods are usually good for about three years, but the original catalytic converter lasted for 12. I would not assume that "new exhaust" included a new catalytic converter.
(2) A 1985 2.5L has a truly awful carburetor, that's partially computer controlled. It also has an EGR valve that can plug up. After 19 years, it would not surprise me if the carburetor is in need of replacement or serious work, and I would also have the EGR checked.
{Edit} Add #3: Any possibility that the choke is sticking in the closed or partially-closed position? That would make it run rich and really choke down the amount of air that could flow through the engine.