I recently put added another 2gb of RAM to my system it was a Corsair VS2GB800D2 G with 5-5-5-18 timings, the thing is my other stick of RAM is 6-6-6-18. How do I overclock the Corsair stick to match the other stick? Thanks.
The board will default to the speed of the slower set.
You won't notice any difference by setting the speed manually to the speed of the faster set, and you may end up getting errors if the slower set cannot handle the faster timings.
I would say if it is working fine, leave it alone and don't worry about it.