S8 engine codes AUX and AYS (USA)
 

I've finally reinstated my Bentley manual and rummaging around noticed that for the D2 S8 it only covers 3 years with 2 engine codes , neither of which I've seen before.
2001 - AUX, 2002/3 - AYS.
My S8 is a 2002 build with AVP engine.

In the unlikely event that I do go delving into the engine myself does anyone know what, if any, the significant differences are between these 3 codes?

AUX doesn't feature in my copy of Etka - AYS does and appears on the same data sheets as AVP, but there are differences (ribbed belt pulley is unique on the first page I hit) so I wouldn't rely on the part numbers being correct....

Its probably just tweaks for the US market or emissions. Etka lists the AYS for the European market as well as AVP & AQH, and shows the heads and cams as different numbers for the AYS v AVP but everything else looks the same. AUX appears to be US only.