340 Intake Manifold Heat Shield

Take a new hack saw blade, attach it to a trimmed down paint mixing stick, use duct tape or whatever.. and saw the bypass nipple down the ID center. Once it is through you can split the nipple off the threads.

YES it is time consuming but, it does work and you save your intake threads without galling them up. Otherwise, you would need to re tap a new thread if you
extract that old nipple and pull the threads out with it.. Heater nipple may have to be re tapped if you muscle it out. Or cut it flush at the hole. and drill out remaining stub. Or die grind the ID out again. You still may end up re tapping the hole.
HR20