a miss at around 2000rpm and is sluggish on a tap of the throttle and burps/pops and backfire at the carb.
u may not have moved any HT leads...To get a back fire thru a carb u NEED an ignition while a firing cylinder is open...
This can only be caused by a couple spark plug wires wrong
or a valve mis adjusted and open...
or cross fire between HT leads
or broken, cracked dirty Dizzy cap rotor.
Check #1 is set to fire on compression stroke (thumb on #1 spark plug hole to feel for the compression stroke)
Check and re check HT lead order.
Inspect rotor/ cap inside and out with a magnifying glass looking forand arc trails / cracks... then clean
Run motor on a dark night and feel/ watch for any arching...
Remove the MSD unit, and with it in hand, walk out of the garage, place your hand as far behind u as possible, then bring your hand in a very fast arch, releasing the msd unit at the right to to accurate it in a manner for greatest distance and height.
Return to the garage and car.
The reasons why, I have expressed several times in old posts.