pipe popping

Ironmike, one more thing to consider...

When it starts popping is it erratic or does it sound more like a constant miss? If it's erratic it could be excess fuel getting into the header pipe. The heat of the pipe with the raw fuel gives a loud pop sound. Looking at your old posts, you mentioned an Edelbrock mechanical pump, are you running the model rated for 6 PSI? If the problem is excess fuel it could be dirt in the needle seat, to high of fuel pump pressure, floats sinking or mis-adjusted. If you have clear sight plugs in your float bowl you can usually see the bowl overfill when it's popping (when the problem is occurring).