BMW Repair: BMW 740i, spark plug wires, spark plug wire

Question
Evan, I have a 1993 740i (I know you specify '99 and newer but I am hoping you can help)which has a recurring problem with moisture accumulating in the coil packs under the covers. The problem is an accumulating one and gets worse the further you drive it - can probably drive 200 -250 km before we need to dry out and start again. It is not coming from the water coolant system and we are at a loss to understand why this keeps happening.
My service agents, who specialise in BMW/Merc repairs have had the car in and out of there centre for a total of 2 months over the last 9 months and cannot determine where the moisture is coming from. I am no expert but it appears like condensation forms under the covers each time the engine is started. When it starts idling roughly the mechanic drys it out and we start again. only to have the problem reoccur within a short space of time.
Any ideas? In desperation, we are contemplating leaving the covers off to see if that solves the problem.
Apart from this the car is in mint condition.
Regards,
Brett

Answer
Brett, this is a M60 engine? Individual coils over each spark plug? No remote coils? No spark plug wires, just the Rubber boots that connect the coils to the spark plugs? In other words 8 coils under the plastic covers? Just want to make sure we are talking apples and apples. I have never worked on this year/model. Is water accumulating in the spark plug bore tubes? What are the Techs drying out? The Coils or the plastic covers? Is this one cylinder or all of them? One Bank? or Both? If it is one cylinder I would remove the coil and make a spark plug wire to connect the coil to the plug. Ground the mounting tab of the coil if needed. Then run the car so you can see down the plug bore and see if the tube fills up with moisture (cylinder head leak, poreious casting). There has to be coolant or some other form of water introduced into the area.
-Evan