Depending which tests the errors are at, you'd need to start playing with vcore, cpu vtt, vdimm and/or memory's main/sub timings.
Memtest86+ v2.11 guide outlines the basics of each test and what errors at those tests represent http://i4memory.com/f79/memtest86-v2-11-a-6/
as does my basic overclocking guide at http://i4memory.com/f83/announcement...y-eva2000.html
outline what voltages correspond to what aspect of an i7/X58 needs tuning.
Now it's a matter of trial and error testing in memtest86+ v2.11 to basically see what voltages and settings result in less or no errors in those specific tests. Pen and paper comes in handy to record what settings/voltages you use and how many errors you receive.
There's 2 ways you can go
1. start at highest mem frequency you can boot into memtest86+ and still get errors (hand full i.e. 1-200 errors), and work your way down, so playing voltages until you get less or no errors. If all settings don't work, then drop mem clocks by another 10-25mhz, and retest again, drop down another 10-25mhz if all voltage combinations don't reduce or eliminate errors
2. start with stable mem frequency and work your way up using memtest86+ by finding what voltage combinations allow you to run high mem frequency. So bumping mem frequency by 10-25mhz at a time keeping voltages same as your stable mem frequency. When errors occur at next bumped mem frequency, play with voltages and find what voltages help reduce or eliminate errors. Then once you've find that mem frequency, bump mem up by 10-25mhz at a time and re-tweak voltages and so on.. and so on.
All trial and error. Over time, you'll get to know which voltage combinations your memory responds to so it will get quicker for memtest86+'ing phase.
You'll end up with a paper full of mem frequency/timings and voltage combinations and how many errors if any each combination has which you can go back to later for further research/tweaking if need be.
Then after that it's windows stability test at those memtest stable frequencies as memtest stable isn't necessarily windows stable as i mentioned at http://i4memory.com/f79/memtest86-v2-11-a-6/