Audi S5 misfire/engine

[Jess123]

My partner has an Audi S5 2008 plate, the engine management light is on, along with the parking brake warning light and the ABS light. He has taken it to an Audi specialist garage near us, however spent nearly £4000 on getting things fixed (all 8 injectors/spark plugs, breather valves, the mass air flow sensor, vacuum lines and the manifold runner arm) and it is still not fixed. I'm concerned they are doing work that isn't the problem to get money and they can't seem to fix it.
He loves the car , but has spent a lot on repairs that haven't fixed it.
If it helps, it also misfires on a cold start, however runs perfectly and doesn't lose power when driving it. The garage did say they didn't think the two were linked, and after taking it in the most recent time and them fixing what they thought was causing an air leak, the lights did stay off for just over a week but came back on yesterday.
Does anyone have any ideas or what it could be?

 

[pelhamsdetailing]

The car would have stored fault codes in the ECU when it came into these issues and posted the warnings lights that you've seen on your dash. It would be worth phoning up the garage you went with and ask if they can provide you word for word the fault codes they found when scanning your car before doing the work.

I'm saying this like they did indeed scan the car before doing work, because logically it's the first thing a garage should do to best understand the problem at hand.

 

[dave_beastttt]

Compression test?

 

[Jess123]

A compression test has apparently been done and everything was fine according to the garage. I initially booked it in for them to check the light, compression test and full vehicle health check. It was running lean when they tested for an air leak, but a seal seems to have fixed this. They did plug it in the ECU, I can't remember the faults that came up however will check with the garage and see if I can get what initially came up. They replaced lots of parts and some of them cleared however one has stayed on throughout and they can't figure out what it is, so are taking the approach of fixing bits and just hoping! But it's beginning to add up now!