Is the cpu lapped? if so lap the TRUE as well, it makes a lot of difference, i used an arctic freezer 7 on my 1.2750 vid q6600, done 3.0ghz on this voltage, i then jumped to 3.4 @1.3750 vcore, then 3.6ghz@ 1.400 vcore, got bored with 3.4 and decided to go higher, this involved lapping the cpu and TRUE and a vcore of 1.50265 in bios, 1.496 windows idle, 1.526 at p95 100%load, coupled with some chipset voltage tweaking on my asus p45 mobo, runs as stable as can be, its probly the best combo ive ever had, when a noob oc'er like me can do this theres hope for anyone

, my clocks, all prime stable can be seen here in this thread mate on the last 2 pages.
http://forums.overclockers.co.uk/showthread.php?t=17779323
This is a record of a lot of the quad core overclocks from various oc members, and its a very good read in its own right, to give an idication of quad overclocking