Kestrel/IIS extremely slow on .NET 4.6.2 - asp.net-core

Question

I have a NET 4.6.2 MVC (Frontend) which talks to a API (backend) via Rest and all of a sudden has become extremely slow on our test server.
Other applications on the server appear fine, and running this application locally it's blinding fast.
I've tested the API at it's end-points and the response time is <10ms (Caching), using NLog, I've got some results from Kestrel and it appears to be stalling at an incoming request.
Looking at the logs, there is a clear 3 seconds where the request comes in and nothing happens.
I'm pretty much lots of ideas here - Could it be a server issue? As it works fine locally?
2016-12-23 16:34:53.5251|1|Microsoft.AspNetCore.Hosting.Internal.WebHost|INFO|Request starting HTTP/1.1 GET http://myApplication.myTestServer.com/Request/Create
2016-12-23 16:34:57.3845|1|Microsoft.AspNetCore.Routing.RouteConstraintMatcher|DEBUG|Route value 'Request' with key 'pageNumber' did not match the constraint 'Microsoft.AspNetCore.Routing.Constraints.IntRouteConstraint'.
2016-12-23 16:34:57.3845|1|Microsoft.AspNetCore.Routing.RouteBase|DEBUG|Request successfully matched the route with name 'default' and template '{controller=Home}/{action=Index}/{id?}'.
2016-12-23 16:34:57.3845|2|Microsoft.AspNetCore.Mvc.Internal.ActionSelector|DEBUG|Action 'myApplication.Controllers.RequestController.Create (myApplication)' with id 'de2f360e-a000-4ff0-94ea-2cff3afb5af1' did not match the constraint 'Microsoft.AspNetCore.Mvc.Internal.HttpMethodActionConstraint'
2016-12-23 16:34:57.3845|1|Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker|DEBUG|Executing action myApplication.Controllers.RequestController.Create (myApplication)
2016-12-23 16:34:57.3845|1|Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker|INFO|Executing action method myApplication.Controllers.RequestController.Create (myApplication) with arguments ((null)) - ModelState is Valid
2016-12-23 16:34:57.4001|2|Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker|DEBUG|Executed action method myApplication.Controllers.RequestController.Create (myApplication), returned result Microsoft.AspNetCore.Mvc.ViewResult.
2016-12-23 16:34:57.4001|2|Microsoft.AspNetCore.Mvc.Razor.RazorViewEngine|DEBUG|View lookup cache hit for view 'Create' in controller 'Request'.
2016-12-23 16:34:57.4001|2|Microsoft.AspNetCore.Mvc.ViewFeatures.Internal.ViewResultExecutor|DEBUG|The view 'Create' was found.
2016-12-23 16:34:57.4001|1|Microsoft.AspNetCore.Mvc.ViewFeatures.Internal.ViewResultExecutor|INFO|Executing ViewResult, running view at path /Views/Request/Create.cshtml.
2016-12-23 16:34:57.4001|5|Microsoft.AspNetCore.DataProtection.KeyManagement.KeyRingBasedDataProtector|TRACE|Performing unprotect operation to key {0c8426b3-7550-4bd9-9f7a-039549bbdf89} with purposes ('C:\Octopus\Applications\UK - Test\myApplication\2016.12.23.163307', 'Microsoft.AspNetCore.Antiforgery.AntiforgeryToken.v1').
2016-12-23 16:34:57.4001|31|Microsoft.AspNetCore.DataProtection.KeyManagement.KeyRingBasedDataProtector|TRACE|Performing protect operation to key {0c8426b3-7550-4bd9-9f7a-039549bbdf89} with purposes ('C:\Octopus\Applications\UK - Test\myApplication\2016.12.23.163307', 'Microsoft.AspNetCore.Antiforgery.AntiforgeryToken.v1').
2016-12-23 16:34:57.4001|6|Microsoft.AspNetCore.Antiforgery.Internal.DefaultAntiforgery|DEBUG|An antiforgery cookie token was reused.
2016-12-23 16:34:57.4157|2|Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker|INFO|Executed action myApplication.Controllers.RequestController.Create (myApplication) in 25.6799ms
2016-12-23 16:34:57.4157|9|Microsoft.AspNetCore.Server.Kestrel|DEBUG|Connection id "0HL1BA65KRN93" completed keep alive response.
2016-12-23 16:34:57.4157|2|Microsoft.AspNetCore.Hosting.Internal.WebHost|INFO|Request finished in 3891.2205ms 200 text/html; charset=utf-8