Hello,
 
I know there have been issues with E8400 temp sensors, but I have significant differences in my core temps.
 
Core 0 reads 56 idle, and Core 1 reads 25 idle.
 
I have a Gigabyte GA-EP35-DS3R mobo, and a Scythe Ninja RevB wiht 1200 rpm fan on it.
 
Temps were tested with both Speedfan and CoreTemp.
 
Any idears?  Should I try to take out the heatsink and reapply thermal paste?
 
 
 
Thanks!

It wouldn't hurt.

With really big heatsinks in tower cases, the weight of the heatsink can be pulling it off one side of the CPU slightly.  Not enough to completely lose contact, but it may mean there's a slightly bigger gap with paste in it than the other side.  I've seen people suspending the heatsink from the top of their cases with velcro straps, and that seems to fix the problem for them.
 
Pressure between the top of the CPU and base of the cooler can make a big change in cooling efficiency.  The Swiftech Apogee GTX improved cooling over the old version by curving the base slightly, so it flattens as pressure is applied, and makes better contact with the whole CPU.

Thanks for the help!  I am currently waiting for a backordered Thermalright LGA775 Bolt-Thru kit to arrive, so that should solve the issue of heatsink pressure.  I will update you all when I get the part and try again!
 
Thanks.