It may help if you added your MY in your signature as don't believe the 4.2 and the 5.0 use the same MAF

From what you've said above you've fitted a MAF recently, if so elaborate please?

Also appreciate that the MAF's fitted to XK's are used on other cars...and crucially Jag don't make MAF's, from memory it's either a Denso, Hella or Bosch part...but others may well correct my assumption if wrong

 

On the 4.2 X150s at least, the MAFs are manufactured by Denso. You can buy them from Jaguar (~£180 each) or Denso (~£92 each), so I deduce that the price of an empty Jaguar parts bag is approximately £88. The Denso part number for a MAF for a 4.2 XKR (probably same as XK but they only need one, XKRs have two) is DMA-0114.

 

Yes dont risk any other brands. Bought denso units for $119 on Amazon over a year ago and never had an issue since
part number Denso 197-6040 this is for 2008 xkr

 

That looks like a cross-reference part number for a Delphi MAF. Just checked again, the official Denso P/N is definitely DMA-0114.

 

Denso 197-6040 is a Denso Maf and it works perfectly on a 4.2 XKR over a year without any problems or check engine light.

 

Denso part catalogue is here - http://www.denso-am.com/e-catalogue/

Interestingly, no results there for the part number you have but it does list the one I used. Google does return hits for both. I'm not disagreeing that you have a correct, working part, just that the OP might have a slightly easier time at their preferred parts supplier if they have the part number that Denso's own catalogue lists.