I had this problem but only on cold starts, when the car warms up the buck is gone, hence fuel trims. I have hks intake and uicp, ssqv. I would definitely say it would be your fuel trims....

 

I turned the adjustment knob down softer on the bov today and it stopped. I can do about 75% throttle with no problems. The bov is mounted to the intake pipe with a hose leading back to the UICP. The adjustment knob is half in my fan. I figured I'd give it a shot before I started buying crap. (sorry, only had car for a few days... still working out the "previous owner" junk.) I can see why it was set where it was. It hits the fan shroud if you put it where it needs to be.

I set it there anyway to stop the surging. Whatta ya know... it stopped.

Fuel trims? C'mon guys...