Bosch double platinum spark plugs #8101...they seem to run the idle a little smoother than the champions that were in 4.0 , but it has 133k when i changed them so I cleaned the throttle body with half a can of B-12 carb cleaner and these new plugs work fine for my Jag.... I got a set of 6 for $30... cheers

 

That's good to hear something after such replacements that makes a sparkling difference