348 TS misfire after service

Had my 348 Serviced the other day for a basic oil service. They said the EVAP needed changing, so got them to do it, but on the way home it was juddering everywhere whilst putting my foot down. It seemed to clear after 20 miles on the motorway, but drive the next day and feels like a misfire and just juddering when I accelerate.Phoned the garage and they said EVAP valve would not do this, so either plugs, coils or dodgy fuel. Is this true, as worked fine before it went for service?

 

The exact description from the garage for the reason to change, is that they smelt fuel and, so they wrote in the quote:

One of the Evap system pipes has come adrift, looks like it has previously been repaired. I would advise we replace this valve and then re test the vehicle.

does this make sense, could it now be a fuel issue, like over/under fuelling, or coils/plugs just suddenly going after being taken for a service?

 

How could I tell if it was faulty without buying a new one. Would this cause juddering when you accelerate?