Got Shell 93 Octane and now barely idles 1973 Dart 340

this is not a comment on the gas...but you need to up the timing....BTDC 2.5 degrees even though is factory spec....the engine will run alot better with more initial advance.
Ok. But I can tell it's not running right. I close the choke and the idle speed shoots up to 1200 rpms. Did something clog a jet? Carb rebuild?