Sorry man but your cams lobes are worn. In the second pic the left hand lobe has the classic signs of no oil. Now that you have the covers off,turn the engine so that a cam lobe is away from the rocker. See if the rockers can wriggled by grabbing them .
Any that can be moved are your loose tappets. If you can push any of the tappets down wards with a hammer they are worn.

If it is the right rear,you have worn cam bearings and no amount of swapping spray rails and denial will fix it because the tappets wont be getting sufficient oil pressure .
I do these engines on a daily basis ,I'm not guessing here. the 560 should be smooth powerful and dead quiet when running.
A blocked up sensor wont affect running in the manner you described. A blocked cat might so get the exhaust pressure tested. If the engine has been running with a blocked cat (the car is 24 years old ..) the oil will have been diluted causing more wear problems stemming from an over rich condition.