Hi Lee, are you talking about the EGR system OR the small bore (approx 1.5" diam) rubber breather pipe that goes from the middle of the top of the engine to the airbox air pipe?
There is no mod for the breather pipe but the mod which removes the EGR valve is useful to do, as it allows the engine to breath clean filtered air and runs smoother as a result.
Direct the breather pipe into a catch tank and block off the hole in the air intake pipe (a wine cork fits but doesn't look OEM). If you are trying to get the engine to run on clean air you must do the EGR and stop oil vapour getting in.