It could also be the distributor. Mine was doing the same thing. Mis-fiting on 2-3-4, and would buck between 1500 and 2500 RPM. I whipped the snot out of it after pulling out in front of someone, and it went away the next day. Previously I had done a full tune up, and the check engine light still came on, and still showed the same codes. After it's beating, I noticed the rough ide went sway, and the next day the check light went off. hAsn't come back on in a week. But my mechanic said distributors are very common to be bad. if it is, try DISTRIBUTOR KING. An OEM unit is about $500.00.
JIM