Mike,
It would depend on what the difference is.
Since the parking area is common area,
VA ยง 55-513 gives the Association the right to make rules regarding common areas. I suspect your governing documents provides this same authority. Therefore, I would simply send the new plan to everyone who purchased three years ago.
Obviously, as Fred pointed out, infractions to the parking rules should be given the benefit of the doubt until the Board knows the new plan has indeed been provided to everyone. I suspect you have already corrected the issue and only the new plan is now being provided in the packages.
One thing we are going to do this year is republish our governing documents to the membership. It will be a bit of expense but there have been enough amendments that we felt it's good to make sure everyone has the same set. You may want to consider doing the same.
Tim