I have a Chevy 305 coupled to a Turbo350.I just put on a new Edelbrock Performer manifold,mild cam,and Demon 525cfm carb.It seems to idle okay,but sometimes when I punch it,the carb back fires.Everytime I punch it at a stop sign,the engine stumbles badly and almost dies.Once the Monte gets going it runs okay.However,at cruising speed sometimes I get a mystery back fire from the carb.What should the timing be,and how about the idle?Could I have bad plug wires?I've done everything the carb manual tells me to do.Any help would be greatly appreciated.