That's just the cam plug. When they line-bore the holes for the camshaft, they bore straight thru. So it has to get plugged. My '86 Jetta head even had a hole like that.

The VTEC solenoid mounts over that hole, but doesn't have anything to do with that. Mine still has the plastic plug. You can't turn an LS head into a VTEC head; there's a lot more that's different.