is it not the egt sensor gone, I hav never had one go myself so don't now the fault that it would throw. but the lambda is the back one. this one is in the front of the up pipe. I am only going off what the garage said but with what you have changed I think it's the maf on the way out in my opinion. but if light stays off and no running problems it could just be a 5 min thing. I had it when a plug from maf came loose. just reset ecg and job done. :D