Could the tuners that carried out the rolling road session not indicate whether its a fuel/spark etc problem?

The plug as reality says is for the electro magnetic pressure actuator, it enrichens the fuelling for boosting and shuts off the fuel supply on over run. It could be fauly although i'd be more inclined to say its the fuelling ECU playing up.

Do you know anyone with any spares that could lend you a pressure actuator and fuelling ECU, they both are very simple to swap