Fault code for lambda and misfires

[Ibiswhite_s3]

I’ve got a s3 8p bhz engine got a few fault codes relating to the lambda sensor 

fault code p3255

fault code p3266

fault code p2237

 

also got a random misfire across all the cylinders.

 

it had a new lambda sensor last October from a main dealer.

 

the car is a stage 2 with 3” downpipe and decat.

 

so only has the one lambda sensor in the downpipe.

 

what’s my issue guys 

Any help would be great