Just manually OC that bitch. I've been running a i5-2500k for months now at 4.2Ghz on only a Hyper 212+ with no problemo.I think Turbo Boost only allows one core to reach 3.8Ghz if I'm not mistaken. If two cores are needed then they each can peak at 3.7Ghz, 3 cores each at 3.6Ghz and all four at 3.5Ghz.
After a bit of investigating via Google I have found a few posts from owners of both Gigabyte and ASUS Z68 mobo owners who have this exact problem. It seems like both Gigabyte and ASUS are enabling this "feature" in order to give their boards a better score with reviewers.