Multiple Ignition Coil failures over the last year
 

Hello all,
Have an 07 E350 with 118k, I changed the plugs at around 114k a year prior with whatever was recommended. Since then I've had to change 2 coil packs (2 and 5), now cylinder 6 is failing (P0356). Anyone know why they are failing like this; is something more serious amiss?

Thanks

Nope---read a good industrial statistics book!!