Thanks for the info, JK. Stock everything.

I will check for loose fittings, as for MAF icing, it would seem unlikely as it has been moderate in temperature (~28F) during these occurances - and never had the problem during the coldest (-20F) days of winter. However, the humidity has been higher, and maybe I am actually melting snow or ice out of the filter that accumulated during the winter? Hmmmm...a new air filter is probably in order...

I have an EGR block-off plate, but not installed on this truck. Recommended, or no? Would it solve this problem, or compound it?