P0414 Everything checks out okay but...!?

Good evening folks,

I have a 2008 xf SV8 with the infamous DTC code P0414....!  It's had much done to it like German remapping, the supercharger fully rebuilt with 10% reducer pully etc etc etc... and it now produces just short of 500bhp... lovely!

However this damn code and engine yellow warning light comes on... only when the engine has partially cooled!  If you stop take on fuel, 9 times out of 10 it won't come on shortly after start-up again.  If you go and do some stuff, like coffee and cake obviously engine temperature drops, virtually every time the engine light comes on and DTC Code P0414 appears.  Go through the clearing system, light out, no code...and off we go again.

This happens pretty much all the time!  I have replaced the secondary valve with new, I've just finished checking electrical connections and the secondary air pump...all working...!  I've checked all the vacuum and air hoses for air leaks...none!  

So, the only thing left is the Secondary Air Injection Pump Check Valve - Jaguar (C2C32933) on top the engine, but after start-up I can hear it ticking (as it should or..?) as it has done for the last three years.  Maybe that too needs replacing?

So my question is, can anyone throw some light on the subject and advise accordingly, is it a faulty sensor or ECU etc.? 

Very much appreciated and thank you in advance for your assistance.

AJ