I have 2000 Dodge Dakota (Origial Owner) 5.9 L 4x4 with 75k miles. Over last 2 years I have noticed it started making a pinging type sound at around 1800 and 2200 rpm under light or heavy load. It will not do it just by reving the engine. The sound has recently gotten much loader. It has tendency to not make the sound while the engin is cold. Not sure if it's related but vehicle does not seem to have the power it used too. The plugs and wires and distributor has recently been replaced. The local mechnic heard the sound while test driving but could not locate the source while on the rack. Suggested possibly the catalytic converter was damaged. Do you think it could be the catalytic converter, or possibly have other ideas?