Bypass hose nipple removal from aluminum intake manifold

I use a acetylene torch and heat the fitting cherry red. Let it cool some then spray penetrating fluid around the threads. You want to do this while its hot but not so hot it burns the fluid as your spraying it on. Its going to smoke so open the doors. After you spray it immediately put a pipe wrench on it.
If its really thin you can heat it cherry red then take a punch and collapse the fitting away from the threads. These methods work 99.9 % of the time on the worst fittings.
If you try turning without heat you risk galling the aluminum threads. At that point you would be stuck using a heli-coil or going with a reducer bushing. Both not great options in this application.