I've read I can remove the BCDD and plug the hole in front of the throttle valve to eliminate the air leak that would result. If I do that, though, what effect will it have on EGR operation?

There's a vacuum tap for the EGR on the throttle assembly right above the BCDD mounting face. I don't know if vacuum for this tap also goes through the BCDD, so that when I plug the BCDD inlet hole, I'll also eliminate the vacuum passage for proper EGR operation.