Unless you change the design characteristics, the coil will only fire at the voltage necessary to bridge the highest form of resistance. You may wish that 30kv would go through those fouled plugs but unless you change the system they will use less voltage than normal plugs (they are fouled and that is what fouled means - basically shorted - less resistance). There are systems that will crank the voltage up, such as capacitive discharge systems. they fire a given voltage no matter what the load. There are also multistrike controllers that fire the plug three or more times each stroke for special purposes. But unless you change the system your plugs will fire at 10kv at idle warm and need maybe as much as 18kv to fire the plug under lean loaded conditions.
Since MBs have no available voltage problems unless the coil is bad, gimics like this are just a waste of money.
Bosch Master, ASE Master, L1
33 years MB technician