Land Rover Repair: S3 4.25l petrol running hot, temperature guage, infrared thermometer

Question
My s3 is running hot and i'm getting the feeling i'm getting close to my original problem so here is the story. recently burnt out an exhast valve in number one cylender. got a full regrind with hardenended valve seats goes great.
but:  Now severly running on (or dieseling )after turn off. ie it will run on for 30 seconds to a minute if you let it.
temperature guage has been dodgy (sometimes works sometimes doesnt) discovered sender was faulty replaced temperature sender. then oh my god is running up near the red all the time no wonder i'v burn't out a valve and it runs on. cooling system seems to work well, radiator is clear of bugs, system retains presure and is full of new coolant. thermostat has been removed, and the flow is good (you can see water swirling arround in the top tank of the radiator. so what can commonly cause hot running on s3? running to lean? how can i check this (an after market holley carboreture is fitted). ehat about timing ??
otherwise is running great. poor idle when cold but i guess thats to be expected.


Answer
In my previous answer one thing I missed was:

Running too lean.

I suggest you use an infrared thermometer to check the temperature at top of radiator, bottom of radiator, and on block.  Look for hot spots and make sure the cooling system is really working.