Ran my Nova today it has a 72 Mark IV 454 in it .Edelbrock torquer 2 intake Holley 3310 vac. sec. carb. Header's around 10.5-1 comp.Not sure of cam but has a lope to it.Advanced my timing to 14 degrees init. ,seems to run a little smoother. It still has a shutter when it is idling , also the timing line moves a little at idle. Could this be in the ignition? It has a H.E.I. with a accel super coil. When cruising at around 1500-2000 the exhaust backfires a little . When you get on it the engine really run's strong. Any help would be appreciated.