03 Chevy Silvarado 1500 4.3L V6 engine problems


I have a 03 silverado with a v6 and when i accelerate to around 2500 rmp, the tach starts going crazy and i hear a clicking noise coming from underneath the vehicle. The thing only acts up after the engine warms up, it has no problems when its cold. I have replaced the cam sensor, the plugs and wires, the distributor, dist. cap, dist. rotor. What else could be causing this?