In a medium bowl, add the cream cheese, mayonnaise, garlic powder, dill pickle juice and vinegar; do not mix yet.
Grate the onion with a microplane or fine grater and add to the bowl; do not mix yet.
Before mixing, chop the pimentos; even the pre-diced ones are a little too big for piping the final filling back into the eggs.
Add pimentos to the bowl and mix well; it is recommended to first mix all ingredients, except the cheese, really well for a better flavor consistency.
Once mixed, grate the extra sharp cheddar cheese and add that to the bowl, doing a quick second mix: the cheese will break up into smaller pieces, but there is no need to have the perfect consistency yet, as the egg yolks are still left to add.
Cut each boiled egg in half, longways, and use a small spoon to pop the egg yolk away from the egg white and into the bowl with the filling.
Rinse the egg whites of any residual yolk; set aside.
Mix the egg yolks into the pimento filling; it should become relatively smooth with only the pieces of pimento and some cheese pieces still intact.
At this point you can spoon the pimento cheese-yolk filling into the egg whites or use a piping bag and to fill the egg whites.
