The second change to the recipe was that I used plain yogurt instead of sour cream, which really brought out the tanginess of the lemon and lime.
The last tweak I made to the recipe was that I used 1.5 tablespoons of poppy seeds instead of the 2 that the orignal recipe called for. You can add the full 2 tablespoons for poppy seeds if you want I can't stop you they're your muffins. I just didn't want to spend all day picking poppy seeds out of my teeth.