Use the following steps to access the performance counters.
On the Desktop, click Start, point to Programs, point to Administrative Tools, and then click Performance.
In the Performance dialog box, click Add.
In the Add Counters dialog box, from the Performance object drop-down list, select from the available BizTalk:Message Agent performance counters, and then click Add.
In the Add Counters dialog box, do one of the following:
After selecting the counters, click Add and then click Close.
For each Host instance,the throttlings state are shown with « Message delivery throttling state » and « Message publishing throttling state »
When there is no throttling, their values are 0. But when they got throttlhing state, their value could be 1 to 11
Here is their definition :
|Message delivery throttling state||A flag indicating whether the system is throttling message delivery (affecting XLANG message processing and outbound transports).
|Message publishing throttling state||A flag indicating whether the system is throttling message publishing (affecting XLANG message processing and inbound transports).
For fixing throttling, start by readung this link http://msdn.microsoft.com/en-us/library/aa559893(BTS.10).aspx
Then I wish you luck