It sounds like there are two conditions being discussed here
1. Popping on deceleration is usually caused by running too lean in the idle to mid range. It is also due to pumping air into your exhaust either through the AI still being in place, or an exhaust leak at the headers, crossover, or slipons. Also can be caused by a vacuum leak but you would notice other symptoms with the vacuum leak.
2. Loud KaPows on startup or when decelerating with the throttle shut off are due to being too rich. There is a fine line between richening your idle screws to reduce popping (which works by the way) and being too rich which causes the mini explosions.
My experience with my 03 BA.
