A demon I assume is like a holley. The accelerator pump adjustment is too tight. The car is getting to much gas . Loosen it up so there is .015 clearence between the arm and the spring. Its the carberator. Just because is new means nothing. also if it vacumn secondaries try changing the spring it sounds like the secondaries are kiccking in too early. If its mech secondaries they could also be kicking in too soon.
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