1997 Mercury Cougar car is misfiring or cutting out

Engine Mechanical problem
1997 Mercury Cougar V8 Two Wheel Drive Automatic 91k miles

I have a 97 cougar with 91k on the clock. Recently I learned about the factory recall on the 4.6 intake manifold leaking coolant. Mine was leaking at the front where the aluminun crossover piece is where the updated ones have now. I replaced the intake with a good used one with the updated crossover piece. New gaskets and theromstat were put in also. Now the engine light stay on and when driving it cuts out and misfires. New plugs were put in as well Ideling it hits on all 8 cylinders. Just when drving this happens. It runs fine for a little bit when driving and then starts the cutting or misfireing. The car was running fine except for the coolant leak before the intake manifold was installed. Do you have ideas what to look for as to what's causing this?