If you look at the engine side of the stock TB then look at the aftermarket one, sometimes there are extra passages that bleed the idle air into the main plenum, so sealing those off and adding a tube to feed the idle air chamber of the manifold is an effort to stabilize the idle air and get rid of the split BLMs. If you redo it, use JB weld or pin it in there so it can't get sucked into the engine.