Look closely at the phase sensor wires to see if disintergrated(inside dizzy).
I would not worry about the colour of the spark, so long as there is a spark.
As you have recently changed the fuel pump, how many miles has it done since ?, have you changed the fuel filter lately.
As the problem started since the pump change, it may be loads of air in the system but this ould cause surging, mine revved up to 3000rpm on it's own after I did mine, which was over ten years old.
Check the voltage at the pump anyway.
Also not meaning to be rude double check the firing order as backfiring is normally ignition timing related.
Just a few ideas
tabetha