Ok so £3000 later, huge amount of diagnostics test at two main fiat dealers and a visit to the successful garage by a Fiat UK specialist, it appears the problem is solved. It turns out the regeneration was not working correctly and the exhaust system basically clogged up. The MAF sensor was fine and while it was kicking up a fault code this was due to a reduced airflow through the system due to the excess deposits. So if you get this issue my advice is to have the regeneration system checked first so the garage don’t was your time and money. If anything changes I will post again.
