Just installed a set of headers and cat back system. Problem is the excessive heat coming off the headers melted the plastic plug wire looms. Also melted the black plastic wire covering going to the temp sensor. They had plenty of clearance, approx. 1.5inches. Has anyone else had this kind of problem??
It makes me wonder how much heat is hitting those brake lines .75inch away!

Any ideas or help would be greatly appreciated.

Hmm, melted the wire looms, shouldn't do that, that's what the loom's are for is to keep heat away from the wires. I had the tubing melt on my temp sensor as well, it had clearance, I don't know whether the heat melted it on or it ended up laying on the header it self. What temp does your car run at?

Were your headers coated?

Are you using 90 degree spark plugs? I do believe some plug wires have hardened connectors designed to withstand the heat from being close to headers.