Memory and BIOS help

CPU: i5-750
MB: P7P55D-E Pro

I installed this RAM into a new build: G.SKILL ECO Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) 1.35v 7-8-7-24-2N ( http://www.newegg.com/Product/Product.aspx?Item=N82E168... ).

The motherboard defaults it to 9-9-9-24 @ 1.5v 133mhz. So when I turn on XMP option, the ram settings are set perfectly but I think the i5-750 compensates for the 133 to 160 increase and overclocks itself. The problem is that this disables the turbo boost feature.

So my question is, can I manually set just the timing to 7-8-7-24 and change the voltage to 1.3500, while leaving it below the advertised mhz to 133 instead of 160 so it wont change cpu settings?

Is there a huge difference in performance from a 9-9-9-24 timing to a 7-8-7-24 timing?

I'm somewhat new to all this, I appreciate any input.

~Hideo