My opinion is one of two things;
A torn inlet hose or FMIC piping leak, or the diverter valve is dumping massive amounts of air back into the loop. I know it dumps after the MAF, but when I was tuning my BOV I had the exact same condition when it was constantly on full recirc when cruising. Try disconnecting the vacuum line at your diverter valve and drive it to see if your surge is gone. Just don't get into any major boost with the valve disconnected.
You may want to try and clean the MAF if none of the above resolves it.