as said above, that vacuum pipe what carries air, senses the air, for a boost cut, and engine load to select a pre programmed ingition curve from the memory of the ecu, but as said a modified ecu can have a altered map to suit setup

hope this helps, put it this way, if it was just a case of removing the pipe, there wouldnt be such things as chipped ESC 11 ecu as all johnny boys would just remove it and we would have alot more blown up rst's around