FEATURE_MaxConnectionsPerServer and FEATURE_MaxConnectionsPer1_0Server are wininet settings (not specific to IE, although IE uses wininet for connection management and thus iexplore.exe can be configured for specific connection handling settings) and editing these will affect IE maximum HTTP 1.1 and 1.0 (respectively) connections per host, per process. IE9 (and IE8) actually use 6 as a default unless it has been edited otherwise (as per
MSDN). IE9 actually has a different change, which is connections per proxy - the limit in IE8 was 6, and in IE9 it is 12. If you are seeing 2 http 1.1 connections to a specific host in a specific IE9 proxy, that would definitely be incorrect behavior, and I would recommend checking the registry as per the linked MSDN article above to make sure something or someone has not added an artificially lower limit to iexplore.exe there.