It turns out the extra sticker on KNC miner heatsinks was not needed. Some users have even reported temperature decreases. More at http://forum.kncminer.com/forum/main-category/hardware/8377-it-should-be-removed-before-the-cooler-is-installed-this-is-a-instalation-quality-check-failure and https://bitcointalk.org/index.php?topic=170332.17340.