GTX 570 SLI awful performance

My system specs:

AMD Phenom II X6 1100t @ stock 3.3ghz
ASUS M4A79 Deluxe
8GB DDR2 1066
2 x MSI GTX 570 sc in SLI
120hz Samsung monitor

Problem:

In BFBC2, when using SLI, I am getting GPU utilization numbers (using MSI Afterburner) that are surprisingly low, averaging around 50%. My framerate sometimes drops below 40, with GPU utilization very low. Disabling SLI actually improves performance (not max framerate, but minimum framerate is much higher, and things run smoother).

I've used a bunch of different drivers, but maybe not EVERY SINGLE ONE that might work... Is there a best driver for SLI under BFBC2?

Also I was looking at a 990fx mobo for SLI but many users are reporting the exact same issue, so it isn't a mobo issue, or a "patched drivers" issue, but something else, likely drivers?