I had another look at the air box on my 2013 ACE 30.1 and the bottom of the air box is physically moulded lower to the left side and it also has a weep hole on the bottom side there (not at the lowest point though) that is not covered by the base plate which supports the air box....so that would likely mean there should be a cap on this 1-1/2 port. I also noted that the bottom of the port hole is not flush with the bottom of the air box which would be a likely requirement for easy water removal. So after 6 years of not having one I guess I should find a replacement or just tape over the opening. Maybe I have been lucky to never have had an issue to date. I also wonder if the MAF sensor on the engine side of the air filter would be affected with extra air coming into the air box, but I have also not had any engine issues since day one (knocking firmly on wood now).