I don't know if it's possible to add 1 or 2 exhaust fans to the top of your case, but like I said before, it helped me around 5-7C under load, and also keeping the mosfet area a lot more cooler than before.
Other than that you can try reapplying your thermal paste. Maybe you applied a bit much so this effects the heat transfer.
Also like I said Turbo Boost is really inefficient and for some reason increases the vcore more than that you would require, so this cause some extra heating. If these temperature values are bothering you (and i know that felling), you can try disabling the setting that boost all cores to 3.9GHz. Probably it's set to "auto" in your bios but I know that it's enabled by default on all MSI z87 mobos (since I'm...