I've also suffered with the engine management warning light coming on, on a 2007 VRS, but only after having driven over 4,000 miles with the gasket fitted without any problems. It happened 3 times over a period of 3 weeks, switching itself off after about 24 hours before re occurring a couple of days later.
As some cars seem to suffer immediately, others never, and some intermittently it might suggest that the 9mm gasket is borderline for EGR volumes. (The 19568 error code).
One theory that my local garage suggested was the change in air density due to the recent cold weather might have caused enough of a variation to triger the light.
Having thought about the problem, I'm trying the 9mm gasket drilled out to 10mm. I've run this for 2 weeks now without any problems, so this may be a solution if your car is affected. I don't seem to loose any significant ammount of the benefits of the 9mm gasket. However, I didn't really have a stutter, but the on/off throttle response is much better.
I included a small table where I've calculated the area of the hole in the gasket. 10mm is 23% bigger than 9mm. Increasing the size can obviously reduces the benefits of having the 9mm hole, but should be much better than the 160% bigger hole that a 14.5mm gasket provides. It may be the case that as each car is slightly different, so the optimum solution requires a bit of an experiment.
It would be interesting to hear any comments, and the results if anyone else who suffers with engine light problems tries this. For instance does 9.5mm cure the problem.
One other thing I noticed. After 4,000+ miles the 9mm gasket was quite sooty on both sides. Was this enough to slightly reduce the 9mm hole size. If the car is sensitive you never know
