Originally Posted by MilanoMan
You will be left with a hole on the intake that you don't use assuming you're installing this on a 96-00 Civic...probably an EX/Si...just put a hose to it and clamp it off so you won't get any vacuum leaks, or if it comes witha plug, plug it off. Don't run with an open hole.
On any modern Honda (fuel injected, that is) there is no problem with a vacuum leak before the throttle body besides the grit/grime issues. MAP systems don't screw up like AFM/MAF systems do in these situations, since MAP (speed/density) systems measure after the throttle body... AFM/MAF systems measure before.