And Elvis was sitting next to Dan Baker in the spaceship, which I thought
was kinda weird, but then they turned to me and said:

Not really likely to be the cause of the problem. The vac advance really
only comes into operation at fairly high engine revs with a small
throttle opening (cruising).

You did set the timing with the vac pipe disconnected, didn't you? -
it'll be well out if you didn't.

As a method of setting the ignition timing, listening to the engine note
whilst twiddling the dizzy is pretty much useless. There is however
another method of setting it - see below.

Pretty easy. run the engine at idle with the strobe pointing at the
timing marks and the vac pipe disconnected. Reconnect the pipe, and you
should see the timing marks advance.

It's important to check the centrifugal advance too. disconnect the vac
pipe, and increase the engine revs gradually. The timing marks should
advance smoothly as the engine speed rises, and return smoothly as the
speed decreases.

Bear in mind that the factory timing figure is basically a guess. It
assumes that you're using a particular octane rating fuel, that you live
in a particular climate, at a particular altitude above hea level, and
that your engine has average amount of wear.

There is an excellent method of setting the timing to what the engine
really requires (and it's a lot cheaper than a session on a dyno). First
of all, make sure that everything else is in good shape - correct points
gap, advance working, mixture correctly adjusted, no air leaks in the
inlet system etc.

Pop a 7/16 spanner in your pocket, and drive out to a nice quiet stretch
of road. Wind the windows down so that you can hear the engine, and let
the car slow down to the slowest that it will go in 4th gear (almost to
the point of stalling). Floor the gas pedal, and listen closely to the
engine.

If you hear the engine 'pinking', stop the car, get out and turn the
dizzy to retard the timing slightly.

If you don't hear the engine 'pinking', get out and advance the timing
slightly.

Repeat this until you find the point where the engine just doesn't quite
pink when labouring with wide open throttle at low speed.

When you get back to the workshop, use the strobe light to make a mark
for future convenience.

May be an obvious question but have you got oil in the carb piston? If it
isnt there, the piston will fly up on rapid throttle opening causing a
moment of excessive fuel delivery.
I doubt its the cause, but worth mentioning.