When I bought my car (99 GT) it had a misfire, took it to my mech, he replaced something on Cyl #3. He said it was a COP, but someone else told me he only replaced the boot. Does replacing a boot fix a misfire, or did he really replace the COP. his is my first Stang so Im not too sure how all this works. Can someone explain the diff between these. Also, Im doing a tune up, what is the benefit of replacing the boots only. Is there any? or should just do the COPs???? Best place to get either besides dealership??? Thanks