Make sure that plugwire is not running next to another, separate it out of the loom. If it still sparks the same way, then throw that plug away and put a new one in.
No it's not the Ecu, not the ballast, not the wiring. It has to be between the rotor and the plug, and my money is on the plug.
BTW
just to be sure, #6 is passenger side, Third from the front right?
