How much engine lowering for pre-cats replacement ?

[ruedisrs6]

Gentlemen,
unfortunately after my problem with massive oil in the cats resulting from a defective return valve in the oil pump module 4 years ago, I am more frequently have a problem with throwing an error code of "cat efficiency too low" on both banks. No other error beside the obligatory secondary air injection error which pops up maybe once a months. I replaced the monitor O2-sensors but unfortunaley no change. The car passed the emission check at TÜV, but I guess the errors are a sign that my pre-cats are fading. The error is currently only thrown during warm up phase, but I want to be prepared when it shows up constantly.
So, has anyone replaced the cats with the engine not dropped ? I found some infos about this in the forum, but I intend to replace all O2-sensors with original ones which means I need to access the connectors mounted on the left side of the transaxle and covered by a heat shield. How much inch do I have to lower the engine/subframe to get access to the O2-sensor connectors ? Do I have to disconnect the tubes from the A/C-compressor or the tubes to and from the oil tank for this ?

Any info appreciated, many thanks !

[ATinOf]

You can query the state of the O2 sensors with VCDS if you have access to one to see what life they have left in them, I'm a bit far away to offer the use of mine!!!

See - https://www.ross-tech.com/vag-com/m_blocks/030-049.html