After driving in stop start traffic today the amber (engine warning?) light came on in my car. I thought it would have turned itself off on my return to the car 10 hours later but it hadn't. I don't know if performance was affected, as I was too wary to try puttting my foot down.

An AA man has checked it and reset it via the OBD port. He said it means the engine is running too rich and could be the air filter ot Lambda sensor. He didn't really elaborate on this but gave the inpression I didn'y need to worry. Can anybody explain what this means? I am taking the car in to get a Green cotton filter and Samco TIP next week. Will this help or hinder the problem?

Looking around on Google it looks like Lambda. Possibly the MAF too.

You should get these fixed before commiting to any more modifications.