Ok i have a HEI, ht 383, newly installed 1 3/4 headers, and a 600cfm edelbrock. Had a slight miss before the headers and now it will kill the car every few full stops(example idle in drive at light fine then drive to next light and dies in drive) after driving it and at high rpm (2500-4600rpm) it has a surge with occasional backfire through carb. Timing is set 10 deg with vacuum advance disconnected and Ive got fresh plugs gaped to .045. Any ideas on what could be causing this?