I posted on your other thread relating to same issue, however this thread tells us that you have had the inlet manifold removed I am guessing it was your Modine cooler hoses you had replaced, these are below the manifold even so you don't have to remove to get to them.

It may be you have an air leak where the manifold has been removed this would cause the rough running thus a high idle.

You don't need to connect diag stuff this just shows easily what is wrong, good fault finding and you can work the problem out. In any case they do have diagnostics but not what they know it as I.E (OBD) it's a simple flash system needing nothing more than a 12V LED or LED and resistor and is quite effective, in any case that won't be a sensor causing this problem.

Martin