The great big MK6 Golf 118TSI tuning thread
Ive never personally seen the cats on a 1.4 twincharge engine, but have many times on Mk5 Golf GTI, Mk6 Golf GTI and Mk6 Golf R (which all appear identical) and can tell you they are a brick wall (very dense and restrictive).
On the GTI and R the downpipes actually have 2 cats - one right up near the turbo (which can be DIY removed easily in about 5 mins to reduce restriction and increase airflow) and a secondary cat down under the car. This secondary cat could be easily cut out and a new hi flowing cat welded in its place.
Surely something along these lines can be done on the 1.4 twin charge?
Pics for inspiration (my Mk6 Golf GTI)
http://www.vwwatercooled.com.au/foru.../02/03ci-1.jpg
http://www.vwwatercooled.com.au/foru.../02/iqxx-1.jpg
http://www.vwwatercooled.com.au/foru.../02/0t9e-1.jpg
http://www.vwwatercooled.com.au/foru.../02/apzm-1.jpg
http://www.vwwatercooled.com.au/foru.../02/l4nq-1.jpg
http://www.vwwatercooled.com.au/foru.../02/hgqp-1.jpg
The great big MK6 Golf 118TSI tuning thread
It will throw a code if you remove the catalyst or if you choose a catalyst that doesn't perform as the oem one does.
The o2 sensor after the cat will sense more environmentally unfriendly emissions and the car will throw a code.
The imitator o2 sensor fools the car into thinking things are ok. Another option is to flash the ecu and tell the car to ignore the error.