Jim McDonald is on the right track with the soft plugs. I once ripped all the emission control goodies off a Fiat Spider (last carbureted model) and plugged all the holes (including EGR) with some nice AN fittings (like the fittings you see on the ends of braided hose). I was working in the parts room of a commuter aircraft hangar at the time and had access to lots of that sort of thing. I think leaving the old injectors in will probably come back to haunt you. Do it right. Give ipd a call. I'm sure the plugs are pretty cheap.