I had a cyl 4 misfire and everyone suggested its because of the location of the crack on my 0331 head. Of course I had all the other symptoms of a cracked head like loosing coolant, milky oil, etc. So the head is now swapped with a Clearwater unit but I'm still getting a little miss/low idle with slight vibration. The current symptom feels just like the original misfire but no code (yet). I'm thinking may be the coil rail is faulty. But since the coil fires cyl 3 and 4 at the same time, a bad coil should cause a lot more power loss and vibration than I'm sensing now. Right?
Is it possible for the coil to go bad on only one cyl? And is there a way to test the rail? Didn't find a procedure in the FSM.

 

Anyone? Appreciate some input before dropping $120 for a new coil rail.
Thanks.