Preheat oven to 350. Grease and flour two 9 inch round cake pans.
Mash sweet potatoes with their heavy syrup in mixing bowl using fork or potato masher. Add cake mix, eggs, oil, and cinnamon. Blend with mixer on low speed for 1 minute. Stop machine and scrape down sides of bowl. Increase mixer speed to medium and beat 2 to 3 minutes more, scraping down sides again, if needed. The batter should look well combined and thickened. Divide batter between prepared pans. Place pans in oven.
Bake cakes until they spring back when lightly pressed with your finger and just start to pull away from edge of pan, 28-31 minutes. Remove pans from oven and place on wire racks to cool for 10 minutes. Run a dinner knife around edge of each layer and invert onto a wire rack. Cool to room temperature.
Place cream cheese and butter in large mixing bowl. Blend with mixer on low speed until combined, 30 seconds. Stop machine. Add confectioners' sugar, a bit at a time, blending with the mixer on low speed until the sugar is well incorporated, 1 minute. Add vanilla, then increase mixer speed to medium and blend the frosting until fluffy, 1 minute more. Fold in coconut and pecans.
Place one cake layer, right side up, on platter. Spread the top with frosting. Place second layer, right side up, on top of the first layer and frost top and sides of cake with clean, smooth strokes.