I have a ford 2000 f 250 i have found the same thing going on but on cylinders five and six changed all coil packs and plugs. i pulled the boot and i found a small order fuel and a rust discoloration (brownish in color). I beliave from smelling and looking that the threads are not tight causeing a blow through on two of the cylinders. This happend once before and i helix coil replacement and the code cleared. And never had a problem again with that coil i gonna do this to cyl 5 & 6 and see if it makes the truck run smother again. i mesured voltage on all good cylinders then macthed to bad cylinders and all the same voltage. I was testing for manifold gasket to have an air leak so i was spraying carb cleaner and listen to hear the engin reave nothing happened so investigated and found to beleaive it is the threads in the alumninum gasket. I will post my result on this.