Re: wont go
fiat or alfa dealer will have an examiner which can do the job nicely. tell them you dont want a simple code read you want a full diagnosis using real time data. they charge by the hour for it, and it usually takes 2 hours so expect to pay £120. WHAT!! thats right its bloody expensive, and all you get is some advice and suggestions and observations.
surely there's a better option? yes there is, use a local diagnostic specialist, often advertised as an auto electrician for some strange reason. cheaper than a dealer and more highly skilled.
i'd try the lambda sensor idea first, at the very least try fitting a scrapyard or ebay £5-10 second hand lambda before you try anything else.