bidirectional interface

Is there any way to tell whether I have created a malevolent bottleneck in a bidirectional interface? What message volume should a bidirectional interface be able to handle? Is there anything that can or should be done to ensure that messages aren’t bumping into each other?

Here is my scenario. I receive messages from two sources, translate them and send to Extenal System. (The external system has the EMPI number.) The external system returns the original message with the addition of the EMPI number. The returned messages are sent static route/raw to an Outbound thread.

The issue is that all messages are received back from the External System. Not all messages received are sent to the Outbound2 thread.

Inbound1–

                Outbound1 <--> External System

Inbound2–        .

                        .

                Outbound2

Any thoughts, ideas, suggestions are always greatly appreciated!!

Kathy