There's a saying among ICE (internal combustion engine) repairmen. "90% of carburetor trouble is ignition.) The basic idea is to be sure the ignition system is working proper before going on to solve carb problems.
I just had a look at the Electrex install instructions and note there is a basic problem. Their timing marks "move" when you rotate the stator to adjust the timing. A fixed, non moving timing mark is needed to accurately verify timing. (Like the original timing pointer in the primary case.)
Also, the rotor is not keyed to the shaft but secured by the grip of a tapered collet. Tapers and collets usually hold just fine if torqued properly but the possibility of slippage is real. It would most likely slip towards being retarded.
So, first check the rotor position relative to TDC as per Electrex instructions and correct if needed. Once properly located, consider pinning it.
Next, arrange a fixed timing pointer and mark the rotor for 34 deg BTDC.
Then, check timing with a timing light between 3000- 4000 rpm and adjust as needed.
Finally, ride it to see what jetting work it needs. (Popping on decel is usually an air leak at the head or a lean idle setting or plugged idle jet.)
Hope this helps.