2001 dodge ram 1500

Looking for a little help. The truck is missing, especially in the 1500-1700 rpm range. It jerks very viloently, and the check engine light goes on and off, and even blinks at me. I've changed the plugs and wires, and now I was wondering if anybody else has an opinion. While idling, you can tell the motor is not "right." It has 90,000 miles on it, and has had the oil changed regularly.
Thanks in advance!!