Everything has been copacetic for over a year, but recently my Holley 390 on the Slant has started stumbling right "AFTER" acceleration. It's not hesitating from idle to go, just slightly stumbling JUST PAST depression of the pedal. Jets, nozzles, accelerator pump, vacuum advance have all been changed earlier with the timing adjusted properly when out of the blue it starts this stumbling. No vacuum leaks. Unhooked the vac advance and plugged the carb tube - had no effect. Timing mark's right on the money (and hasn't been changed). Hot/cold, doesn't matter. It even stumbles at slow cruising speeds (below about 50mph) right after mashing the gas. Worked perfectly and started this without anything else being changed. What say you?