Here is a photo of the hole that goes into the AS&M 58 MM throttle body, the top port where the plate bolts above too.
What is its function for the throttle body.

This is the bottom part of the throttle body where the IAC gets additional air for the idle air passageways modified for my stroker motor.

 

That hole connects to the small rectangular chamber, under the top cover plate. The passenger side of that chamber is where the vent line to the passenger side valve cover connects. When the PCV system is working correctly, clean, MAF measured air enters the hole in the throttle body, goes to the valve cover, where its pulled through the crankcase and lifter valley by the PCV system vacuum.

When the PCV system get overloaded, the pressure starts to build in the crankcase, and the pressure vents out the valve cover, through the top of the throttle body, and out the hole in the picture. That's how the throttle body and intake manifold gets coated with oil.

 

Thanks, So this wouldnt affects BLMS/IAC etc for a speed density engine?

 

If the crankcase was pressured and venting into the throttle body (before the blades), it could change the temperature of the air entering the throttle body slightly.... which would cause a very minor difference between the IAT sensor reading used for the speed-density calculation, but it would be too small a difference to even notice. You would have more of a problem from the oil entrainment, because oil reduces the effective octane rating of the fuel.

Operating correctly, it should not affect anything, because its in front of the blades.