[lovehamr]

I'll take a whack at this.
I think the only time someone washes their cylinder walls with a DP it's because some adjustments are not right. Think about it, with the tuneability of the accelerator pump circuit (shooters, pump cams, pump size etc.) there should be none of that. To put that into perspective, think about all those engines running Webers. If it were just the number of accelerator pumps which were evil then those engines would be toast by the third run. The engine only needs enough fuel during throttle opening to cover the lean condition until the main circuit has responded to the change in throttle opening and subsequent change in manifold vacuum. If the shooters are the right size with the right pump cams, then over fueling won't happen.

Since I can't tell when the smells are coming from the pipes I'll just say that the transient nature of the accelerator pumps usually don't have much to do with an over rich smell from the pipes. For that I would look more at the idle settings and the main circuit. What jets are in the carb?

The "banging and popping on the overrun" are usually due to exhaust leaks which may account for some of the exhaust smell as well.

Just some places to start, Steve