would check the pcv breather pipe work for cracks, how many miles has it done , if over 60k when was timing chain done last, pinking tends to be a timing issue ie retarded, also codes for cat tend to be related to chain causing it ie unburnt fuel air mix being dumped on the honey comb burning oil can also cause it, as if been driven a long time with timing out can over heat the valves and melt stem seals or at very worst effect piston rings, this said you need a process,
compression test 150-175 is common, oil pressure worth checking 60psi when hot is good, low oil pressure can effect timing as vanos runs off oil pressure, timing chain needs to be checked, rocker cover off and see how far the tensioner is out of body, 10mm borderline 14mm its bin time. can use a camera on endoscope and point it towards rear or engine in the oil filler hole, or use autocom cdp plus software and read the vanos prescribed positions and actual,, all this really should of been done from the very start of the issue to know what state the engine is in,, also if you find 1 and 4 cylinders and 2 and 3 cylinder the compression at same as each other but different to the other two if that makes and compression move around a lot chain is prob on last legs and tensioner is at its max just before it pop out and bends all the valves .
