I'd try the TBS needles at this point. They really help out the mid range. Although, technically, I don't think they affect idle, which is where your decel popping is coming from. It just seems that a 48 pilot would be big.
Also, you can change your jets without pulling the carbs if you have in brent's hex screw kit for your carb. I can rejet in under 30 minutes easy.
How bad is the popping? Download the Specialty Spares video on my site (link in my sig) and pay attention the the first stop I come to. There is popping as I slow down. Mine doesn't pop nearly that bad anymore. Is yours popping more less than my vid?
