A.net takes a look at the OCZ EL Gold PC4000 2GB Kit in their latest review. Below is a direct quote from the review:

"Upon first receiving the modules, I set my CPU multi down and the memory divisor to 1:1, then stepping up 5Mhz at a time at 2.8v, I reached 275Mhz. Stepping up the voltage to 2.9v, I was able to boot Windows and benchmark at 280Mhz. Knowing that most modules overclocking behavior differs after some use, I ran the modules at 270Mhz on 2.8v for almost a week. "



Link: OCIA