[Jake Raby]

There is a good reason why the OEM tubes are non-metallic.

Consider where stray spark will travel from cracked coil packs if a metallic (conductive) tube is employed. As it stands now cracked coils will generally not cause misfires because they stray spark can't discharge into any conductive material nearby. With a metallic tube that is not the case and stray spark will discharge into the tubes and that can create collateral damage, just like it does in Cayenne engines where it kills oil level senders and other electronics when the coil packs crack.

Stray spark can also take out the drivers of other items when it has a path to ground. It is entirely possible that stray spark charging a metallic spark plug tube could even take out the driver in the ECU for that particular coil pack.

Considering how bad these coil packs are with failures, I'd be concerned. With stray spark near variocam solenoids and etc I'd be concerned with those items and their drivers also being damaged.

Just think about it.