2003 XJR with 185,000 miles has been getting random engine failsafe and traction control unavailable warning. The car will then run but be extremely restricted from having any power. If I shut the car off for a few minutes, everything is fine and I may not get the error again for a week or two. I took to my mechanic and he scanned and gave me the code P0430 and thinks that the oxygen sensors are showing slow to respond. However, another person I trust feels it has more to do with the Cat Converter. I would appreciate any ideas.
Thank you

 

TRAC fault is an ABS issue - possible solution is module repair. But this can also be linked to the throttle as the car goes into failsafe. Look at cleaning all the connectors on the throttle body.

The P0430 is catalyst efficiency below threshold B bank (2)