Hi Ron,
I see from your user info that you are a new member of UKAT. After a while you will repeatedly read "more information required" or "what tests have you done?". Another question that will probably be asked, so I will get in first , is why did you change the air temp sensor? That is not to say it wasn't faulty but the answer may help to separate symptoms and cause, which could also be said for the HO2S.
"Any ideas?"
Yes, loads, ign, injectors, fuel pressure, exhaust or inlet leaks, valves, rings, pcv, evap system the list goes on, so you need to eliminate much and then look at what is left.
I personally cannot help you much as I have almost no knowledge of these engines, but I do believe that Lambda is very high on some of these when in stratified mode, so full gas readings might help someone decide if they are "perfect" at high idle.
HTH's,
Bryan.