I had posted this information on another thread that may be helpful to some others, based on the number of previous postings on that thread.

I fought engine clatter in my '97 XLT 4X4 for months before finally asking the Ford dealer for help. After diagnostics found nothing, they removed a two pin plug (for lack of a better word) from a dead leg cable that they called an octane compensator. They showed me where the cable was in case I wished to replace it later, but I don't know if it was exposed before I took it in. Anyway, it is located on the firewall directly behind the battery. It comes from a cable harness and is quite short, maybe 2", so they may have pulled it out and left it. In the end of it is a small gray plug with part number E53B 14A624-0. With the plug removed, I have had no clattering, which usually occurred under load or climbing in high gear on the highway. They warned that I might lose a bit of power, but I haven't really noticed, and gas mileage remains at about 15 MPG. I replaced it once, just out of curiosity, and sure enough the clatter was back. I promptly removed it and put back in my console where it has been for two years.

Hope this helps a few folks out there. Please let me know if anyone gets the same results!!