Paul - you were right. No hairline cracks but big one width of coil pack on 1/4 side which is towards engine. On closer inspection after cleaning found several more large cracks on other side too. Wonder it was running as well as it was
GREAT advice. Thank you
It was probably the original coilpack.
My other piece of advise to you now would be to replace it with a MOTORCRAFT DG536 coilpack. Yes they are a bit more $ than the parts store/aftermarket units but well worth it in my opinion. I would tell you to shop around but there is a lot of counterfeit Motorcraft parts out there now. I would not buy from Amazon or ebay. I would trust Rockauto, and online Ford dealer (such as Tascaparts.com, etc) or you local ford dealer.