Spark plug wire melting

Hi, I keep having problems with the spark plug wire melting. It is always cylinder three that melts the plug wire. I replaced the plugs twice. Last time I did it I replaced the plugs the wires and the coil packs. I am still having the same issue. The original plug wires had metal boots. I am wondering if that would cause the plugs to burn up being that they sit so close to the manifold. The plugs are the same length as the original ones but do not have the metal insulator on it. The original ones I did not have a problem with I just had to do a tune up. Could it be the plugs or could it be something else? I also have a catalytic converter code. I am having the catalytic converters replaced tomorrow with high flow catalytic converters. I took it to an exhaust shop and that is what they recommended. Being it would be easier to change them out. Thanks.