Replace 2004+ with +

I'm trying to replace a prefix 2004+ with a +. Any idea why this is not working please? do you think the HMR should be to delete 2004 instead of action replace?  

 

sip-manipulation
        name                                    DeletePrefix
        description                             Delete prefix 2004+
        split-headers                           
        join-headers                            
        header-rule
                name                                    StripReqUriPrefix
                header-name                             request-uri
                action                                  manipulate
                comparison-type                         case-sensitive
                msg-type                                out-of-dialog
                methods                                 INVITE
                match-value                             
                new-value                               
                element-rule
                        name                                    FixReqUri
                        parameter-name                          
                        type                                    uri-user-only
                        action                                  replace
                        match-val-type                          any
                        comparison-type                         pattern-rule
                        match-value                             ^\2004+
                        new-value                               $ORIGINAL-^"2004+"+"+"