Drill the vent hole anyway in the cap. You need it with a full tank on takeoff. Obviously fuel blocks the new vent and fuel pressure goes down which is kind of scary on a take off. It will stabilize when you level out and burn fuel. There is no problem with the cap vented too.
John, you remember correctly, but the step was removed with the 12/27/2013 revision that added a fuel tank vent line.
Here is screenshot of the relevant instructions from a 2011 version of section 37.