Ok so I did a little tweaking over the holidays and managed to get 3.8ghz stable at rather surprising voltages. It passes over 6hours of p95 large fft's and over 8hours of p95 blends and I ran 20 runs of Intel BurnTest @maximum stress and it passed with flying colours.

CPU-Z and CoreTemp (it was pretty cold in my room during the stress test, it usually gets around 65c under full load in intel burntest)


Best runs in Intel BurnTest


Bios Settings:
Frequency:
CPU Clock Ratio: 19x
QPI Clock Ratio: 32x
Base Clock: 200mhz
Memory Multi: 10x

Memory Timings: (memory is rated; 2000mhz@1.6v, 9-9-9-27)
Cas Latency Time: 9
tRCD: 9
tRP: 9
tRAS: 24

Voltage Settings:
CPU Vcore: 1.16875v
QPI/Vtt: 1.150v (1.1v is stable for lower memory frequencies)
PCH Core: 1.050v
CPU PLL: 1.700v
DRAM: 1.600v

Advance CPU features:
Intel Turbo Boost Tech: Disabled
C1E Support: Enabled
C3/C6/C7 Support: Enabled
CPU EIST: Enabled

Oh and my i5-750 is from Batch#L937B557, I picked it up late last year. Also my motherboard is a Gigabyte P55A-UD4.