I solved this problem.. just thought I would share it.

I installed rksports ecotec intake and it came with some flimsy hose to go from the intake to the crankcase breather port (or something like that... little outlet on left front of engine.) I put it on and drove, but i soon noticed considerable air-puffng squeaky noises. It drove me nuts until i found a kink in this hose, which was causing the problem. I got a thicker-walled hose and, voila, solved. So if you have the rksport intake, there ARE NOT mice under the hood.