Backfiring with Rich Exhaust Gas Smell

[frosty0910]

Hi all,

I own a 2014 Polo 6R GTI and I'm facing a problem where the car backfires and pops during deceleration, accompanied by a rich-smelling exhaust. I'm dealing with an engine fault code P2178, which reads "System too rich off idle bank 1." So far, I've replaced the MAP sensor and the pre-cat oxygen sensor. I've also checked the high pressure actual and specified values using VCDS, which are stable. However, nothing works to fix the issue. Can anyone shed some light on this or suggest a fix?