The aluminum heatsheild between the headers and the Air Conditioning compressor, can and break and start to rattle and commonly many owners have them removed. However as a result in warm weather the compressor may shut off. The heatsheild itself may be retained by re-inferencing it and alleviating it of its ability to rattle. However the catalytic converter can yield an inherent ability to generate acoustic resonance. This is often caused by a fault with the mid catalytic converter bracket.