I stopped using fixed vcore and started using offset and my results have much better. At first, I was having temperature issues at stock voltage 4GHz, so I reseated my Hyper 212+ and redid the thermalpaste. Temperatures are 10 degrees lower now.
On stock voltage, 4.5GHz (i5 2500k)seems stable.
However, through 1 run of IBT, my temps jumped to 96C. Any ideas?
You have either a measurement problem (bad application reporting), bad thermal paste install, or there's too much voltage pouring into that chip. What type of offset are you running? I can run +0.005v offset which is almost identical to automatic voltage at stock and hold 4.5Ghz on my 2600k.
IBT is going to heat that chip up more than anything you'll ever do to it. But there's still an issue.
You may need to reseat that HSF again! But first, make sure your temperatures are right. Try a few different applications and see what type of temperatures and voltages you're reading. I'd imagine you're either not seated correctly or it is tossing too many volts at it. If your 212 is seated right it should be able to hold that processor at full load with 1.35v under 80-85C