well, i didn't buy a new coil. i talked to a ford tech., and he told me basically that if my car still ran good, it was okay and that they rarely wear out.
i put in oem platinum motorcraft plugs. $4.85/pce.
i also used oem motorcraft wires which were pre-cut and identical to what came out. they wholeheartedly clicked onto the coil. $34.95/set
i can't imagine what the motorsport wires for $50 would have over oem wires (other than a flashy name and color). spark is spark in a little zetec.
the car runs noticeably smoother. the stock plugs and wires that came off it looked very good. plugs were a little burnt at spark contact, but would have gone probably 25K more miles. even so, the car said it could go 100K miles w/o a tune-up, and it did. ready for another 200K.
