This car has always hesitated (at least) or pinged (at worst) when taking off from a dead stop.

When I did the engine swap, I figured that problem was gone for good. After all, the "new" engine came valve cover to oil pan, exhaust to intake, including the distributor. (I reused the original intake to maintain the existing wiring.)

But it's still there. That tells me it's electronic. Knock sensor? I cleaned the flame trap, but maybe that still? Valve and ignition timing are all spot on now. All new cap/wires/rotor/plugs/batt cables.

What else should I be looking for?

TIA!