Dodge Repair: 1992 Dodge Colt (mitsubishi), spark plug wires, colt mitsubishi

Question
Have 1992 Dodge Colt-import, auto transmission.  Car starts and idles fine when cold.  After warming up it will begin hesitating upon acceleration and will shudder when idling in gear.
 Had to replace cracked exhaust manifold one month ago.  The two center spark plug wires were crossed but happy with gas mileage (33mpg) until the extreme lost of power when the manifold failed.  Car has new air filter, new plugs and wires, new fuel filter, and oxygen sensor.  Could the exhaust system need replacing and how to test properly?  What else should I check?

Answer
check the intake manifold for cracks or leaks; an easy way to do this would be take something like wd40, and while it is running, slightly spray some around the intake contact and mounting areas; if you hear the engine speed up, then you have found your leak; BE SURE NOT TO USE ANYTHING FLAMMABLE..............

good luck / let me know / millec1@bellsouth.net