Glad you got it figured out, Chris. I thought for some reason you had checked all the obvious so I didn't mention it originally, and as you found out- always start with the basics!
As for the popping when cold- you could try turning the idle mixture screws out ½ or 1 turn, but that should really only affect the mixture at idle so a step bigger set of idle jets are probably what's needed. I would go up as little as you can- Aircooled.net has idle jets in 1/2 sizes (42½, 47½ etc) 'cause you reallly don't need to go up very much.
http://vwparts.aircooled.net/W...dle-Jets-p/74405.htm
You'll have to know what size jets are in your carbs now (it's always a good idea to have written down what's in your carbs so you know) and these-
http://vwparts.aircooled.net/W...R-p/jc-4313-0-pr.htm
so you can change the idle jets without removing the carbs are a good idea, and they make it easier to pull a jet for cleaning (should 1 get plugged) as well!
Hope this helps. Al