Ok, here is my setup.

E6600 @ 3ghz
8800GT's in SLI
Gigabyte 650i mobo 8x/8x

Fresh reformat Windows 7 Ultimate 64-bit
Latest drivers from nvidia 190.38
Latest SLI Enhancement patch

Running Crysis Warhead at 1920x1200 Mainstream settings no AA
Using the FBWH BenchTool from guru3d utilizing the ambush flyby benchmark
I get 41 FPS with SLI disabled and 38 with it enabled.

Whats going on?
Thanks in advance