1998 Dodge Stratus engine vibration

I have 1998 Dodge Stratus with 2.4 4cyl that has a vibration or throbbing that transmits to the hole car. It continues from idle to high rev and the motor seems to have a loud tapping noise when cold. The mileage is at 107540 and the only past reairs have been tune ups and regular maintanace. But recently the vibration started along with a loader exhaust sound which tuned out to be a cracked exhaust manifold which I have replaced. I have checked the spark plugs and they are all at a light choco color and the serpintine belt is new. And the alt, air, power steering are smooth and not binding. The engine mount seam to be ok and exhaust system is not touching to body. The temp seems to be ok and no smoking from oil. The fuel mileage is at an average of 26 to 29 mpg. Please help if you can.