Please could you be more precise? Also could you kindly upload some snapshot about "elapsed in the trace"?
As far as I know the phase "Request sent to target server" in the trace includes the time taken for:
1. Message Processor to establish connection with the Target/Backend Server.
2. If it is a secure connection, then it includes the complete SSL Handshake process.
3. Message Processor to send the request payload to the Target/Backend Server.