Soak corn in husks in a large pot of water for at least 30 minutes. This will bring moisture to the corn and will help the corn steam in the husks while on the grill.
In the meantime, make the sauce by mixing lime juice, mayo, sour cream, black pepper and garlic powder. Place in fridge for later use.
Preheat your grill to medium-low heat. Add corn with husks to the grill and close lid. Flip corn every few minutes for about 15 minutes.
Carefully remove husks and place corn back on the grill over medium heat for a few minutes on each side until you have nice grill marks. Then, transfer corn to a plate.
Using a basting brush, brush all sides of the corn with the sour cream mixture. Sprinkle with fresh chopped cilantro and chili powder. Enjoy!
Notes
I cut corn in half to serve. This is completely optional :)