Polara_68

All of a sudden, the basically stock 318 in my ‘68 Polara won’t idle..
In Neutral it “idles” at 300 RPM (or less).
I have to give it throttle to keep it running
(forget about it idling in Drive)...
It was running great, then it stalled on me when slowing down for a traffic light.
I coasted her to the curb and she fired right back up but wouldn’t idle.
I had to nurse her home using one foot on the brake & one on the gas
and throwing it into Neutral at redlights.
It’s almost like the idle speed or Timing were suddenly turned way down
(but the distributor clamp is tight).
It doesn’t run well below 2000 RPM - sounds like a bit of a light, choppy misfire.
She smooths out above 2000 RPM, but power output seems down a bit.
This just happened yesterday evening during normal driving -
since then I’ve verified that the dist. vacuum advance works,
there are no leaking vacuum hoses, the carb & intake bolts are tight,
the floats in the Carter 2-bbl haven’t “sunk”, the power valve isn’t stuck,
no dirt in the needle & seat and the fuel pump is fine (I knew it wasn’t the fuel pump).
The fuel filter is new (old one wasn’t bad, either).
The plugs are 1 yr old and are textbook-perfect in appearance
(as are the wires and cap & rotor).
I converted her to electronic ignition last year using all new components
& a new Mopar electronic ignition wiring harness.
She’s been running like a champ (if you drove it you wouldn’t think it was just a 318,
so says my buddy who owns big-block Mopars) but all of a sudden she won’t idle
& runs poorly below 2000 RPM, and power output seems down..
I have an idea what might be wrong but I don’t want to taint your thoughts/theories..
All responses appreciated..
Thanks!