Weird memory story

I upgraded my processor and memory from a 2.53 133 FSB and 2700 memory at 166 4/5 ratio to a 3.2 200 FSB and 3200 memory.
When I installed the parts a 3.2 runs at 200 FSB but the 3200 memory runs at 160 5/4 ratio.

There is no adjustments in the bios for memory ratio as it is a Dell, is there anyway to manipulate the memory ratio, can I get a Custom bios to perform this because it's a pain in the a$$ to have $280 OCZ 3200 Platinum rev2 running at 2700

I researched this issue and here is what I found in case anybody has the same issue,

Dells are sold with cas 3 400 memory and if you try to install cas 2 or 2.5 the motherboard will default to 333

how much of a performance hit is cas 3 as opposed to cas 2? Is there anyway to work around this problem with custom bios?