With 105k miles, can the coil packs be tested to see if they are still within spec? Should I just fork out $240 for the Ford Performance set? Change out plugs for a "colder" set, since there are 100k miles? Copper, Iridium, Platinum.? My guess is just replace the coil packs and use Ford Performance oem platinum plugs. What did you do, and are you happy with the money spent?