Ive had the same issuse with Fords....If that is the case with the bulbs, start checking grounds as one may have failed leading the ECU to "find" a ground to use. (using the bulbs as one maybe)
A while back I had an IS350 with a very random misfire in cyl # 4. Well after a week of diag, I actually found a connector that the ground were not stripped out and just crimped into the connector. Stripped the wires, re connected them to the connector and walla!! fixed. After that, I got dam near all of the IS's with that issue.....