how to send header parameter to remote syslog ?

You could do something like this:

when CLIENT_ACCEPTED {
   set hsl [HSL::open -proto UDP -pool syslog_server_pool]
}
when HTTP_REQUEST {
    Log HTTP host and request as local7.info; see RFC 3164 Section 4.1.1 - "PRI Part" for more info
   HSL::send $hsl "<190> [IP::local_addr] [HTTP::host] [HTTP::uri]\n"
}

See: https://devcentral.f5.com/wiki/iRules.HSL__send.ashx