[RJT-SS]

It sounds like your wires may have been the problem as you said you are now ok. Another common problem with spark plugs and header installs is that some people do not remove the plugs to do the install. It is not necessary to remove them but, since they are made of ceramic, they can crack if hit by the stock manifold during removal or the header during installation. The symptom of a cracked plug is similar to what you originally described. The only way to check for a cracked plug is to remove each plug and visually inspect the white ceramic part. If it is cracked, the crack usually appears as a dark line.

To remove the plugs, use a 5/8" spark plug socket. It is a deep socket that has a rubber insert in it to grab and hold the tip of the plug. This helps to keep the plug from falling out of the socket (and cracking) after it is fully un-threaded.

When installing plugs, some folks like to put some anti-seize compound on the threads to make future plug removal easier. However, it is not necessary. The torque spec for the plugs is 11 ft lbs but most people do not use a torque wrench. When you tighten a spark plug, you can feel a definite "stop" as you make the final tightening turns. There is no need to over tighten.

Hope this info helps your understanding a little better.