red92civic

well one of my peeps has a 92 honda civic htach with an b18a1 block and a 94 head. The motor is rebuilt. Now the car tends to stutter and bog after certain rpms like about 3 to 4 thousand. Now the goods is that he has replaced distributor, spark plugs, wires, o2 sensor, and fuel filter. Car is still doing the same please someone help me to figure this out.